<PAGE>
 
     As filed with the Securities and Exchange Commission on June 12, 1998.
                                                           Registration No. 333-
--------------------------------------------------------------------------------

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                            ----------------------
                                        
                                   FORM S-8
                            REGISTRATION STATEMENT
                                     Under
                          The Securities Act of 1933

                            ----------------------
                                        
                           OEC MEDICAL SYSTEMS, INC.
            (Exact Name of Registrant as Specified in its Charter)

                            ----------------------
<TABLE>
<S>                                      <C>
            Delaware                                   94-2538512
(State or Other Jurisdiction of          (I.R.S. Employer Identification Number)
 Incorporation or Organization)
 
      384 Wright Brothers Drive
        Salt Lake City, Utah                              84116
(Address of Principal Executive Offices)                (Zip Code)
</TABLE>

                            ----------------------
                           OEC Medical Systems, Inc.

                          1998 STOCK OPTION PLAN, AND
 1993 Employee Incentive Stock Acquisition Plan, as Amended and Restated, and
                    1990 Stock Option/Stock Purchase Plan 
                          (Full Titles of the Plans)

                            ----------------------

                                Randy W. Zundel
 Executive Vice President, Chief Operating Officer and Chief Financial Officer
                           OEC Medical Systems, Inc.
                           384 Wright Brothers Drive
                           Salt Lake City, UT  84116

                    (Name and Address of Agent for Service)

                                (801) 328-9300
         (Telephone Number, Including Area Code, of Agent for Service)

                            ----------------------
                                 With Copy to:

                              Holland & Hart LLP
                       215 South State Street, Suite 500
                        Salt Lake City, UT  84111-2346
                                (801) 595-7800
                        ATTENTION:  DAVID R. RUDD, ESQ.
--------------------------------------------------------------------------------
<PAGE>
 
                        CALCULATION OF REGISTRATION FEE
===============================================================================
<TABLE>
<CAPTION>
<S>                                              <C>                <C>                  <C>                <C> 
                                                                    Proposed             Proposed
                                                                    Maximum              Maximum
                                                 Amount to          Offering             Aggregate           Amount of
Title of Each Class of Securities to be              be             Price Per            Offering           Registration
Registered/1/                                    Registered           Share               Price                 Fee
------------------------------------------------------------------------------------------------------------------------
1998 Stock Option Plan,
  Common Stock,
    $.01 par value                               1,350,000          $21.97/2/            $29,659,500          $ 8,750
                                                                         
1993 Employee Incentive Stock
Acquisition Plan, as amended and
restated,
  Common Stock,
    $.01 par value                                 250,000          $18.67/3/            $ 4,667,500          $ 1,377

1990 Stock Option/Stock Purchase
Plan, as amended and restated,
  Common Stock,
    $.01 par value                                 500,000          $ 9.44/4/            $ 4,720,000          $ 1,353
                                               --------------------------------------------------------------------------
TOTAL                                            2,100,000               --              $39,047,000          $11,519
==============================================================================================================================
</TABLE>

   /1/  Pursuant to Rule 416(a) under the Securities Act of 1933, as amended
        (the "Securities Act"), this Registration Statement shall also cover any
        additional shares of the Registrant's Common Stock, $.01 par value (the
        "Common Stock"), which are issued or become issuable under the OEC
        Medical Systems, Inc. 1998 Stock Option Plan and the OEC Medical
        Systems, Inc. 1993 Employee Incentive Stock Acquisition Plan, as amended
        and restated, to prevent dilution resulting from any stock dividend,
        stock split, recapitalization or other similar transaction.

   /2/  Calculated in accordance with Rule 457(h) under the Securities Act,
        based upon the average of the high and low prices of the Common Stock as
        reported on June 9, 1998, on the New York Stock Exchange.

   /3/  Calculated in accordance with Rule 457(h) under the Securities Act,
        based upon 85% of the average of the high and low prices of the Common
        Stock as reported on June 9, 1998, on the New York Stock Exchange.

   /4/  Calculated in accordance with Rule 457(h) under the Securites Act based
        on the average exercise price per share for outstanding options.


                                       2
<PAGE>
 
                                    PART II

Item 3.      Incorporation of Certain Documents by Reference.
             ------------------------------------------------ 

     The following documents filed by OEC Medical Systems, Inc. (the
"Registrant") with the Securities and Exchange Commission are hereby
incorporated by reference in this Registration Statement:

     (a)  The Registrant's latest Annual Report, filed pursuant to Section 13(a)
of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), on Form
10-K, for the fiscal year ended December 31, 1997.

     (b)  The Registrant's Quarterly Report on Form 10-Q for the quarter ended
March 31, 1998.

     (c)  The Registrant's Registration Statement No. 1-09983 on Form 8-A filed
on June 27, 1991 which includes a description of the Registrant's $.01 par value
common stock (the "Common Stock"), and Amendment No. 1 thereto on Form 8,
Registration No. 1-09983, filed on July 19, 1991.

     All documents filed subsequent hereto by the Registrant pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of
a post-effective amendment which indicates that all securities offered have been
sold or which deregisters all securities then remaining unsold, shall also be
deemed to be incorporated by reference herein and to be a part hereof from the
date of filing of such documents.

     The consolidated financial statements of the Registrant as of December 31,
1997 and 1996, that are included in the Registrant's Annual Report on Form 10-K
for the year ended December 31, 1997, and incorporated by reference in this
Registration Statement, have been audited by Deloitte & Touche LLP, independent
auditors, as stated in their report, which is incorporated herein by reference.
Such financial statements are, and audited financial statements to be included
in subsequently filed documents will be, incorporated herein in reliance upon
the reports of Deloitte & Touche LLP pertaining to such financial statements (to
the extent covered by consents filed with the Securities and Exchange
Commission), and upon the authority of such firm as experts in accounting and
auditing.

Item 4.      Description of Securities.
             ------------------------- 
     Not applicable.

Item 5.      Interests of Named Experts and Counsel.
             -------------------------------------- 
     Not applicable.

Item 6.      Indemnification of Directors and Officers.
             -----------------------------------------

     Section 145(a) of the Delaware General Corporation Law (the "DGCL")
provides in relevant part that "a corporation shall have power to indemnify any
person who was or is a party or is threatened to be made a party to any
threatened, pending or completed action, suit or proceeding, whether civil,
criminal, administrative or investigative (other than an action by or in the
right of the corporation) by reason of the fact that he is or was a director,
officer, employee or agent of the corporation, partnership, joint venture, trust
or other enterprise, against expenses (including attorneys' fees), judgments,
fines and

                                       3
<PAGE>
 
amounts paid in settlement actually and reasonably incurred by him in
connection with such action, suit or proceeding if he acted in good faith and in
a manner he reasonably believed to be in or not opposed to the best interests of
the corporation, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his conduct was unlawful."  With respect to
derivative actions, Section 145(b) of the DGCL provides in relevant part that
"[a] corporation shall have power to indemnify any person who was or is a party
or is threatened to be made a party to any threatened, pending or completed
action or suit by or in the right of the corporation to procure a judgment in
its favor. . .{by reason of his service in one of the capacities specified in
the preceding sentence} against expenses, (including attorneys' fees) actually
and reasonably incurred by him in connection with the defense or settlement of
such action or suit if he acted in good faith and in a manner he reasonably
believed to be in or not opposed to the best interests of the corporation and
except that no indemnification shall be made in respect of any claim, issue or
matter as to which such person shall have been adjudged to be liable to the
corporation unless and only to the extent that the court in which such action or
suit was brought shall determine upon application that, despite the adjudication
of liability but in view of all the circumstances of the case, such person is
fairly and reasonably entitled to indemnity for such expenses which the court
shall deem proper."

     The Registrant's Restated Bylaws provide for indemnification of any
director or officer of the Registrant who is or was involved in any manner in
any threatened, pending, or completed investigation, claim, action, suit or
proceeding, whether civil, criminal, administrative or investigative by reason
of the fact that such director or officer is or was serving as a director or
officer of the Registrant or is or was serving another entity as a director,
officer, employee, fiduciary or agent at the request of the Registrant, against
all expenses and liabilities actually and reasonably incurred by such director
or officer in connection with such proceeding.  Indemnification is limited in
certain instances involving "hostile" takeover actions by members of the
Registrant's Board of Directors and in circumstances constituting a breach or
default under a Company agreement.

     The Registrant's Restated Bylaws also provide that the Registrant will
indemnify its directors, officers, employees and other agents to the fullest
extent permitted by Delaware law.

Item 7.      Exemption from Registration Claimed.
             ----------------------------------- 
     Not applicable.

                                       4
<PAGE>
 
  Item 8.   Exhibits.
            ---------
  Regulation S-K                       Document
  --------------                       --------
     Exhibit                                   
     -------

       4.1         Certificate of Incorporation, as amended.
                   Incorporated by reference to the OEC Medical Systems,
                   Inc. Form 10-K, filed March 30, 1994.
                  
       4.2         Restated By-Laws, as amended May 15, 1997.
                   Incorporated by reference to the OEC Medical Systems,
                   Inc. Form 10-Q, filed August 8, 1997.
                  
       4.3         OEC Medical Systems, Inc. 1998 Stock Option Plan.
                  
       4.4         OEC Medical Systems, Inc. 1993 Employee Incentive
                   Stock Acquisition Plan, as amended and restated.
                  
       4.5         Rights Agreement, dated as of June 20, 1988, between
                   Diasonics, Inc. and Bank of America NT&SA.
                   Incorporated by reference to Exhibit 4.3 of the
                   Diasonics, Inc. Form 8-K, filed August 1, 1988.
                  
       4.6         Diasonics, Inc. 1979 Stock Option Plan, amended and
                   restated as of June 1, 1982. Incorporated by
                   reference to Exhibit 10.6 of the Diasonics, Inc.
                   Registration Statement on Form S-8, filed May 2, 1983.
                  
       4.7         OEC Medical Systems, Inc. 1990 Stock Option/Stock Purchase
                   Plan. Incorporated by reference to Exhibit 99.1 of the OEC
                   Medical Systems, Inc. Form S-8, filed on September 30, 1993
                   (the "1993 S-8").
                  
       4.8         Warrant for the Purchase of Common Shares issued to
                   PaineWebber R&D Partners II, L.P., as amended.
                   Incorporated by reference to the OEC Medical Systems,
                   Inc. Form 10-K, filed on March 30, 1994.
                  
       4.9         Form of Option Agreement used in connection with
                   non-qualified options having service-vesting
                   provisions granted under the Discretionary Option
                   Grant Program.
                  
       4.10        Form of Option Agreement used in connection with
                   non-qualified options having milestone vesting
                   provisions granted under the

                                       5
<PAGE>
 
                        Discretionary Option Grant Program.

              4.11      Form of Option Agreement used in connection with
                        incentive stock options.

              4.12      Form of Option Agreement used in connection with
                        options granted under the Automatic Option Grant
                        Program.

              4.13      Note and Stock Pledge Agreement between Ruediger
                        Naumann-Etienne and OEC Medical Systems, Inc., dated
                        September 5, 1995. Incorporated by reference to the
                        OEC Medical Systems, Inc. Form 10-K, filed April 1,
                        1996.

              4.14      Form of Warrant Agreement used in connection with
                        grant to independent contractors for the purchase of
                        common shares. Incorporated by reference to the OEC
                        Medical Systems, Inc. Form 10-K, filed March 27, 1997.

              4.15      Agreement dated December 17, 1996, to acquire full
                        ownership of Barwig Medizinische Systeme GmbH (BMS).
                        Incorporated by reference to the OEC Medical Systems,
                        Inc. Form 10-K, filed March 27, 1997.

              4.16      Form of Incentive Stock Option Agreement-Initial Grant
                        to be generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan, Incorporated by reference to
                        Exhibit 99.2 of the 1993 S-8.

              4.17      Form of Incentive Stock Option Agreement to be generally
                        used in connection with the 1990 Stock Option/Stock
                        Purchase Plan. Incorporated by reference to Exhibit 99.3
                        of the 1993 S-8.

              4.18      Form of Non-Qualified Stock Option Agreement-Initial
                        Grant to be generally used in connection with the 1990
                        Stock Option/Stock Purchase Plan. Incorporated by
                        reference to Exhibit 99.4 of the 1993 S-8.

              4.19      Form of Non-Qualified Stock Option Agreement to be
                        generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan. Incorporated by reference to
                        Exhibit 99.5 of the 1993 S-8.

              4.20      Form of Stock Option Agreement (Non-Employee Director)
                        to be generally used in connection with the automatic
                        option grant program of the 1990 Stock Option/Stock
                        Purchase Plan. Incorporated by reference to Exhibit 99.6
                        of the 1993 S-8.

              4.21      Form of Stock Option Agreement-Direct Stock Purchase to
                        be generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan. Incorporated by reference to
                        Exhibit 99.7 of the 1993 S-8.

              4.22      Form of Stock Option Adjustment Agreement used in
                        connection with the 1990 Stock Option/Stock Purchase
                        Agreement. Incorporated by reference to Exhibit 99.8 of
                        the 1993 S-8.

              5         Opinion of Holland & Hart LLP, as to the legality of
                        securities being registered.

              23.1      Consent of Deloitte & Touche LLP,  Independent
                        Auditor.

              23.2      Consent of Holland & Hart LLP (contained in 
                        Exhibit 5).

              24        Power of Attorney (included on page 8 of this
                        Registration Statement).
 
        -----------------

                                       6
<PAGE>
 
Item 9.      Undertakings.
             ------------ 
       (a)   The undersigned Registrant hereby undertakes:

             (1)  To file, during any period in which offers or sales are being
             made, a post-effective amendment to this registration statement to
             include any material information with respect to the plan of
             distribution not previously disclosed in the registration statement
             or any material change to such information in the registration
             statement.

             (2)  That, for the purpose of determining any liability under the
             Securities Act, each such post-effective amendment shall be deemed
             to be a new registration statement relating to the securities
             offered therein, and the offering of such securities at that time
             shall be deemed to be the initial bona fide offering thereof.

             (3)  To remove from registration by means of a post-effective
             amendment any of the securities being registered which remain
             unsold at the termination of the offering.

       (b)   The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act that is incorporated by reference in this registration statement
shall be deemed to be a new registration statement relating to the securities
offered therein, and the offering of such securities at that time shall be
deemed to be the initial bona fide offering thereof.

       (c)   Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.

                                       7
<PAGE>
                                   SIGNATURES


     Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Salt Lake, State of Utah, on June 12, 1998.

                              OEC Medical Systems, Inc.


                              /s/ Randy W. Zundel
                              -----------------------------------
                              Randy W. Zundel
                              Executive Vice President, Chief Operating
                              Officer & Chief Financial Officer

                               POWER OF ATTORNEY
                                        
     KNOW ALL PERSONS by these presents that each person whose signature to this
Registration Statement appears below hereby constitutes and appoints Randy W.
Zundel, as his true and lawful attorney-in-fact and agent, with full power of
substitution, to sign on his behalf individually and in the capacity stated
below, and to perform any acts necessary to be done in order to file all
amendments and post-effective amendments to this Registration Statement, and any
and all instruments or documents filed as part of or in connection with this
Registration Statement or the amendments thereto and each of the undersigned
does hereby ratify and confirm all that such attorney-in-fact and agent, or his
substitutes, shall do or cause to be done by virtue hereof.

     Pursuant to the requirements of the Securities Act of 1933, the
Registration Statement has been signed below by the following persons in the
capacities indicated on June 12, 1998:


           Signature                 Title
           ---------                 -----      

/s/Ruediger Naumann-Etienne    Chairman of the Board
---------------------------
Ruediger Naumann-Etienne

/s/Gregory K. Hinkley          Director
--------------------------- 
Gregory K. Hinkley

/s/Benno P. Lotz               Director
---------------------------  
Benno P. Lotz

/s/Alan W. May                 Director
---------------------------  
Alan W. May

/s/Chase N. Peterson           Director
---------------------------  
Chase N. Peterson

/s/Joseph W. Pepper            President, Chief Executive Officer and Director
---------------------------    (Principal Executive Officer)
Joseph W. Pepper

                                       8
<PAGE>
/s/Randy W. Zundel        Executive Vice President, Chief Operating Officer and 
---------------------     Chief Financial Officer (Principal Financial
Randy W. Zundel           and Accounting Officer)
                          

                                       9
<PAGE>
 
                           OEC MEDICAL SYSTEMS, INC.

                                 EXHIBIT INDEX

                                        
Regulation S-K                   Document
--------------                   --------
   Exhibit                        
   -------

    4.1        Certificate of Incorporation, as amended.
               Incorporated by reference to the OEC Medical Systems,
               Inc. Form 10-K, filed March 30, 1994.

    4.2        Restated By-Laws, as amended May 15, 1997.
               Incorporated by reference to the OEC Medical Systems,
               Inc. Form 10-Q, filed August 8, 1997.

    4.3        OEC Medical Systems, Inc. 1998 Stock Option Plan.

    4.4        OEC Medical Systems, Inc. 1993 Employee Incentive
               Stock Acquisition Plan, as amended and restated.

    4.5        Rights Agreement, dated as of June 20, 1988, between
               Diasonics, Inc. and Bank of America NT&SA.
               Incorporated by reference to Exhibit 4.3 of the
               Diasonics, Inc. Form 8-K, filed August 1, 1988.

    4.6        Diasonics, Inc. 1979 Stock Option Plan, amended and
               restated as of June 1, 1982. Incorporated by
               reference to Exhibit 10.6 of the Diasonics, Inc.
               Registration Statement on Form S-8, filed May 2, 1983.

    4.7        OEC Medical Systems, Inc. 1990 Stock Option/Stock
               Purchase Plan.  Incorporated by reference to 
               Exhibit 99.1 of the Diasonics, Inc.  Form S-8, filed
               on September 30, 1993 (the "1993 S-8").

    4.8        Warrant for the Purchase of Common Shares issued to
               PaineWebber R&D Partners II, L.P., as amended.
               Incorporated by reference to the OEC Medical Systems,
               Inc. Form 10-K, filed on March 30, 1994.

    4.9        Form of Option Agreement used in connection with
               non-qualified options having service-vesting
               provisions granted under the Discretionary Option
               Grant Program.

    4.10       Form of Option Agreement used in connection with
               non-qualified options having milestone vesting
               provisions granted under the 


                                       10
<PAGE>
 
                        Discretionary Option Grant Program.

              4.11      Form of Option Agreement used in connection with
                        incentive stock options.

              4.12      Form of Option Agreement used in connection with
                        options granted under the Automatic Option Grant
                        Program.

              4.13      Note and Stock Pledge Agreement between Ruediger
                        Naumann-Etienne and OEC Medical Systems, Inc., dated
                        September 5, 1995. Incorporated by reference to the
                        OEC Medical Systems, Inc. Form 10-K, filed April 1,
                        1996.

              4.14      Form of Warrant Agreement used in connection with
                        grant to independent contractors for the purchase of
                        common shares. Incorporated by reference to the OEC
                        Medical Systems, Inc. Form 10-K, filed March 27, 1997.

              4.15      Agreement dated December 17, 1996, to acquire full
                        ownership of Barwig Medizinische Systeme GmbH (BMS).
                        Incorporated by reference to the OEC Medical Systems,
                        Inc. Form 10-K, filed March 27, 1997.

              4.16      Form of Incentive Stock Option Agreement-Initial Grant
                        to be generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan, Incorporated by reference to
                        Exhibit 99.2 of the 1993 S-8.

              4.17      Form of Incentive Stock Option Agreement to be generally
                        used in connection with the 1990 Stock Option/Stock
                        Purchase Plan. Incorporated by reference to Exhibit 99.3
                        of the 1993 S-8.

              4.18      Form of Non-Qualified Stock Option Agreement-Initial
                        Grant to be generally used in connection with the 1990
                        Stock Option/Stock Purchase Plan. Incorporated by
                        reference to Exhibit 99.4 of the 1993 S-8.

              4.19      Form of Non-Qualified Stock Option Agreement to be
                        generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan. Incorporated by reference to
                        Exhibit 99.5 of the 1993 S-8.

              4.20      Form of Stock Option Agreement (Non-Employee Director)
                        to be generally used in connection with the automatic
                        option grant program of the 1990 Stock Option/Stock
                        Purchase Plan. Incorporated by reference to Exhibit 99.6
                        of the 1993 S-8.

              4.21      Form of Stock Option Agreement-Direct Stock Purchase to
                        be generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan. Incorporated by reference to
                        Exhibit 99.7 of the 1993 S-8.

              4.22      Form of Stock Option Adjustment Agreement used in
                        connection with the 1990 Stock Option/Stock Purchase
                        Agreement. Incorporated by reference to Exhibit 99.8 of
                        the 1993 S-8.

              5         Opinion of Holland & Hart LLP, as to the legality of
                        securities being registered.

              23.1      Consent of Deloitte & Touche LLP,  Independent
                        Auditor.

              23.2      Consent of Holland & Hart LLP (contained in 
                        Exhibit 5).

              24        Power of Attorney (included on page 8 of this
                        Registration Statement).


         -----------------

                                       11
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{"company-data": {"conformed-name": "OEC MEDICAL SYSTEMS INC", "cik": "0000317814", "assigned-sic": "3844", "irs-number": "942538512", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-56769", "film-number": "98647575"}, "business-address": {"street1": "384 WRIGHT BROTHERS DRIVE", "city": "SALT LAKE CITY", "state": "UT", "zip": "84116", "phone": "8013289300"}, "former-company": {"former-conformed-name": "DIASONICS INC", "date-changed": "19920703"}}
As filed with the Securities and Exchange Commission on June 12, 1998.
                                                           Registration No. 333-
--------------------------------------------------------------------------------

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                            ----------------------
                                        
                                   FORM S-8
                            REGISTRATION STATEMENT
                                     Under
                          The Securities Act of 1933

                            ----------------------
                                        
                           OEC MEDICAL SYSTEMS, INC.
            (Exact Name of Registrant as Specified in its Charter)

                            ----------------------
Delaware                                   94-2538512
(State or Other Jurisdiction of          (I.R.S. Employer Identification Number)
 Incorporation or Organization)
 
      384 Wright Brothers Drive
        Salt Lake City, Utah                              84116
(Address of Principal Executive Offices)                (Zip Code)
----------------------
                           OEC Medical Systems, Inc.

                          1998 STOCK OPTION PLAN, AND
 1993 Employee Incentive Stock Acquisition Plan, as Amended and Restated, and
                    1990 Stock Option/Stock Purchase Plan 
                          (Full Titles of the Plans)

                            ----------------------

                                Randy W. Zundel
 Executive Vice President, Chief Operating Officer and Chief Financial Officer
                           OEC Medical Systems, Inc.
                           384 Wright Brothers Drive
                           Salt Lake City, UT  84116

                    (Name and Address of Agent for Service)

                                (801) 328-9300
         (Telephone Number, Including Area Code, of Agent for Service)

                            ----------------------
                                 With Copy to:

                              Holland & Hart LLP
                       215 South State Street, Suite 500
                        Salt Lake City, UT  84111-2346
                                (801) 595-7800
                        ATTENTION:  DAVID R. RUDD, ESQ.
--------------------------------------------------------------------------------
CALCULATION OF REGISTRATION FEE
===============================================================================
Proposed             Proposed
                                                                    Maximum              Maximum
                                                 Amount to          Offering             Aggregate           Amount of
Title of Each Class of Securities to be              be             Price Per            Offering           Registration
Registered/1/                                    Registered           Share               Price                 Fee
------------------------------------------------------------------------------------------------------------------------
1998 Stock Option Plan,
  Common Stock,
    $.01 par value                               1,350,000          $21.97/2/            $29,659,500          $ 8,750
                                                                         
1993 Employee Incentive Stock
Acquisition Plan, as amended and
restated,
  Common Stock,
    $.01 par value                                 250,000          $18.67/3/            $ 4,667,500          $ 1,377

1990 Stock Option/Stock Purchase
Plan, as amended and restated,
  Common Stock,
    $.01 par value                                 500,000          $ 9.44/4/            $ 4,720,000          $ 1,353
                                               --------------------------------------------------------------------------
TOTAL                                            2,100,000               --              $39,047,000          $11,519
==============================================================================================================================
/1/  Pursuant to Rule 416(a) under the Securities Act of 1933, as amended
        (the "Securities Act"), this Registration Statement shall also cover any
        additional shares of the Registrant's Common Stock, $.01 par value (the
        "Common Stock"), which are issued or become issuable under the OEC
        Medical Systems, Inc. 1998 Stock Option Plan and the OEC Medical
        Systems, Inc. 1993 Employee Incentive Stock Acquisition Plan, as amended
        and restated, to prevent dilution resulting from any stock dividend,
        stock split, recapitalization or other similar transaction.

   /2/  Calculated in accordance with Rule 457(h) under the Securities Act,
        based upon the average of the high and low prices of the Common Stock as
        reported on June 9, 1998, on the New York Stock Exchange.

   /3/  Calculated in accordance with Rule 457(h) under the Securities Act,
        based upon 85% of the average of the high and low prices of the Common
        Stock as reported on June 9, 1998, on the New York Stock Exchange.

   /4/  Calculated in accordance with Rule 457(h) under the Securites Act based
        on the average exercise price per share for outstanding options.

                                       2
PART II

Item 3.      Incorporation of Certain Documents by Reference.
             ------------------------------------------------ 

     The following documents filed by OEC Medical Systems, Inc. (the
"Registrant") with the Securities and Exchange Commission are hereby
incorporated by reference in this Registration Statement:

     (a)  The Registrant's latest Annual Report, filed pursuant to Section 13(a)
of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), on Form
10-K, for the fiscal year ended December 31, 1997.

     (b)  The Registrant's Quarterly Report on Form 10-Q for the quarter ended
March 31, 1998.

     (c)  The Registrant's Registration Statement No. 1-09983 on Form 8-A filed
on June 27, 1991 which includes a description of the Registrant's $.01 par value
common stock (the "Common Stock"), and Amendment No. 1 thereto on Form 8,
Registration No. 1-09983, filed on July 19, 1991.

     All documents filed subsequent hereto by the Registrant pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of
a post-effective amendment which indicates that all securities offered have been
sold or which deregisters all securities then remaining unsold, shall also be
deemed to be incorporated by reference herein and to be a part hereof from the
date of filing of such documents.

     The consolidated financial statements of the Registrant as of December 31,
1997 and 1996, that are included in the Registrant's Annual Report on Form 10-K
for the year ended December 31, 1997, and incorporated by reference in this
Registration Statement, have been audited by Deloitte & Touche LLP, independent
auditors, as stated in their report, which is incorporated herein by reference.
Such financial statements are, and audited financial statements to be included
in subsequently filed documents will be, incorporated herein in reliance upon
the reports of Deloitte & Touche LLP pertaining to such financial statements (to
the extent covered by consents filed with the Securities and Exchange
Commission), and upon the authority of such firm as experts in accounting and
auditing.

Item 4.      Description of Securities.
             ------------------------- 
     Not applicable.

Item 5.      Interests of Named Experts and Counsel.
             -------------------------------------- 
     Not applicable.

Item 6.      Indemnification of Directors and Officers.
             -----------------------------------------

     Section 145(a) of the Delaware General Corporation Law (the "DGCL")
provides in relevant part that "a corporation shall have power to indemnify any
person who was or is a party or is threatened to be made a party to any
threatened, pending or completed action, suit or proceeding, whether civil,
criminal, administrative or investigative (other than an action by or in the
right of the corporation) by reason of the fact that he is or was a director,
officer, employee or agent of the corporation, partnership, joint venture, trust
or other enterprise, against expenses (including attorneys' fees), judgments,
fines and

                                       3
amounts paid in settlement actually and reasonably incurred by him in
connection with such action, suit or proceeding if he acted in good faith and in
a manner he reasonably believed to be in or not opposed to the best interests of
the corporation, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his conduct was unlawful."  With respect to
derivative actions, Section 145(b) of the DGCL provides in relevant part that
"[a] corporation shall have power to indemnify any person who was or is a party
or is threatened to be made a party to any threatened, pending or completed
action or suit by or in the right of the corporation to procure a judgment in
its favor. . .{by reason of his service in one of the capacities specified in
the preceding sentence} against expenses, (including attorneys' fees) actually
and reasonably incurred by him in connection with the defense or settlement of
such action or suit if he acted in good faith and in a manner he reasonably
believed to be in or not opposed to the best interests of the corporation and
except that no indemnification shall be made in respect of any claim, issue or
matter as to which such person shall have been adjudged to be liable to the
corporation unless and only to the extent that the court in which such action or
suit was brought shall determine upon application that, despite the adjudication
of liability but in view of all the circumstances of the case, such person is
fairly and reasonably entitled to indemnity for such expenses which the court
shall deem proper."

     The Registrant's Restated Bylaws provide for indemnification of any
director or officer of the Registrant who is or was involved in any manner in
any threatened, pending, or completed investigation, claim, action, suit or
proceeding, whether civil, criminal, administrative or investigative by reason
of the fact that such director or officer is or was serving as a director or
officer of the Registrant or is or was serving another entity as a director,
officer, employee, fiduciary or agent at the request of the Registrant, against
all expenses and liabilities actually and reasonably incurred by such director
or officer in connection with such proceeding.  Indemnification is limited in
certain instances involving "hostile" takeover actions by members of the
Registrant's Board of Directors and in circumstances constituting a breach or
default under a Company agreement.

     The Registrant's Restated Bylaws also provide that the Registrant will
indemnify its directors, officers, employees and other agents to the fullest
extent permitted by Delaware law.

Item 7.      Exemption from Registration Claimed.
             ----------------------------------- 
     Not applicable.

                                       4
Item 8.   Exhibits.
            ---------
  Regulation S-K                       Document
  --------------                       --------
     Exhibit                                   
     -------

       4.1         Certificate of Incorporation, as amended.
                   Incorporated by reference to the OEC Medical Systems,
                   Inc. Form 10-K, filed March 30, 1994.
                  
       4.2         Restated By-Laws, as amended May 15, 1997.
                   Incorporated by reference to the OEC Medical Systems,
                   Inc. Form 10-Q, filed August 8, 1997.
                  
       4.3         OEC Medical Systems, Inc. 1998 Stock Option Plan.
                  
       4.4         OEC Medical Systems, Inc. 1993 Employee Incentive
                   Stock Acquisition Plan, as amended and restated.
                  
       4.5         Rights Agreement, dated as of June 20, 1988, between
                   Diasonics, Inc. and Bank of America NT&SA.
                   Incorporated by reference to Exhibit 4.3 of the
                   Diasonics, Inc. Form 8-K, filed August 1, 1988.
                  
       4.6         Diasonics, Inc. 1979 Stock Option Plan, amended and
                   restated as of June 1, 1982. Incorporated by
                   reference to Exhibit 10.6 of the Diasonics, Inc.
                   Registration Statement on Form S-8, filed May 2, 1983.
                  
       4.7         OEC Medical Systems, Inc. 1990 Stock Option/Stock Purchase
                   Plan. Incorporated by reference to Exhibit 99.1 of the OEC
                   Medical Systems, Inc. Form S-8, filed on September 30, 1993
                   (the "1993 S-8").
                  
       4.8         Warrant for the Purchase of Common Shares issued to
                   PaineWebber R&D Partners II, L.P., as amended.
                   Incorporated by reference to the OEC Medical Systems,
                   Inc. Form 10-K, filed on March 30, 1994.
                  
       4.9         Form of Option Agreement used in connection with
                   non-qualified options having service-vesting
                   provisions granted under the Discretionary Option
                   Grant Program.
                  
       4.10        Form of Option Agreement used in connection with
                   non-qualified options having milestone vesting
                   provisions granted under the

                                       5
Discretionary Option Grant Program.

              4.11      Form of Option Agreement used in connection with
                        incentive stock options.

              4.12      Form of Option Agreement used in connection with
                        options granted under the Automatic Option Grant
                        Program.

              4.13      Note and Stock Pledge Agreement between Ruediger
                        Naumann-Etienne and OEC Medical Systems, Inc., dated
                        September 5, 1995. Incorporated by reference to the
                        OEC Medical Systems, Inc. Form 10-K, filed April 1,
                        1996.

              4.14      Form of Warrant Agreement used in connection with
                        grant to independent contractors for the purchase of
                        common shares. Incorporated by reference to the OEC
                        Medical Systems, Inc. Form 10-K, filed March 27, 1997.

              4.15      Agreement dated December 17, 1996, to acquire full
                        ownership of Barwig Medizinische Systeme GmbH (BMS).
                        Incorporated by reference to the OEC Medical Systems,
                        Inc. Form 10-K, filed March 27, 1997.

              4.16      Form of Incentive Stock Option Agreement-Initial Grant
                        to be generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan, Incorporated by reference to
                        Exhibit 99.2 of the 1993 S-8.

              4.17      Form of Incentive Stock Option Agreement to be generally
                        used in connection with the 1990 Stock Option/Stock
                        Purchase Plan. Incorporated by reference to Exhibit 99.3
                        of the 1993 S-8.

              4.18      Form of Non-Qualified Stock Option Agreement-Initial
                        Grant to be generally used in connection with the 1990
                        Stock Option/Stock Purchase Plan. Incorporated by
                        reference to Exhibit 99.4 of the 1993 S-8.

              4.19      Form of Non-Qualified Stock Option Agreement to be
                        generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan. Incorporated by reference to
                        Exhibit 99.5 of the 1993 S-8.

              4.20      Form of Stock Option Agreement (Non-Employee Director)
                        to be generally used in connection with the automatic
                        option grant program of the 1990 Stock Option/Stock
                        Purchase Plan. Incorporated by reference to Exhibit 99.6
                        of the 1993 S-8.

              4.21      Form of Stock Option Agreement-Direct Stock Purchase to
                        be generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan. Incorporated by reference to
                        Exhibit 99.7 of the 1993 S-8.

              4.22      Form of Stock Option Adjustment Agreement used in
                        connection with the 1990 Stock Option/Stock Purchase
                        Agreement. Incorporated by reference to Exhibit 99.8 of
                        the 1993 S-8.

              5         Opinion of Holland & Hart LLP, as to the legality of
                        securities being registered.

              23.1      Consent of Deloitte & Touche LLP,  Independent
                        Auditor.

              23.2      Consent of Holland & Hart LLP (contained in 
                        Exhibit 5).

              24        Power of Attorney (included on page 8 of this
                        Registration Statement).
 
        -----------------

                                       6
Item 9.      Undertakings.
             ------------ 
       (a)   The undersigned Registrant hereby undertakes:

             (1)  To file, during any period in which offers or sales are being
             made, a post-effective amendment to this registration statement to
             include any material information with respect to the plan of
             distribution not previously disclosed in the registration statement
             or any material change to such information in the registration
             statement.

             (2)  That, for the purpose of determining any liability under the
             Securities Act, each such post-effective amendment shall be deemed
             to be a new registration statement relating to the securities
             offered therein, and the offering of such securities at that time
             shall be deemed to be the initial bona fide offering thereof.

             (3)  To remove from registration by means of a post-effective
             amendment any of the securities being registered which remain
             unsold at the termination of the offering.

       (b)   The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act that is incorporated by reference in this registration statement
shall be deemed to be a new registration statement relating to the securities
offered therein, and the offering of such securities at that time shall be
deemed to be the initial bona fide offering thereof.

       (c)   Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.

                                       7
SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Salt Lake, State of Utah, on June 12, 1998.

                              OEC Medical Systems, Inc.

                              /s/ Randy W. Zundel
                              -----------------------------------
                              Randy W. Zundel
                              Executive Vice President, Chief Operating
                              Officer & Chief Financial Officer

                               POWER OF ATTORNEY
                                        
     KNOW ALL PERSONS by these presents that each person whose signature to this
Registration Statement appears below hereby constitutes and appoints Randy W.
Zundel, as his true and lawful attorney-in-fact and agent, with full power of
substitution, to sign on his behalf individually and in the capacity stated
below, and to perform any acts necessary to be done in order to file all
amendments and post-effective amendments to this Registration Statement, and any
and all instruments or documents filed as part of or in connection with this
Registration Statement or the amendments thereto and each of the undersigned
does hereby ratify and confirm all that such attorney-in-fact and agent, or his
substitutes, shall do or cause to be done by virtue hereof.

     Pursuant to the requirements of the Securities Act of 1933, the
Registration Statement has been signed below by the following persons in the
capacities indicated on June 12, 1998:

           Signature                 Title
           ---------                 -----      

/s/Ruediger Naumann-Etienne    Chairman of the Board
---------------------------
Ruediger Naumann-Etienne

/s/Gregory K. Hinkley          Director
--------------------------- 
Gregory K. Hinkley

/s/Benno P. Lotz               Director
---------------------------  
Benno P. Lotz

/s/Alan W. May                 Director
---------------------------  
Alan W. May

/s/Chase N. Peterson           Director
---------------------------  
Chase N. Peterson

/s/Joseph W. Pepper            President, Chief Executive Officer and Director
---------------------------    (Principal Executive Officer)
Joseph W. Pepper

                                       8
/s/Randy W. Zundel        Executive Vice President, Chief Operating Officer and 
---------------------     Chief Financial Officer (Principal Financial
Randy W. Zundel           and Accounting Officer)
                          

                                       9
OEC MEDICAL SYSTEMS, INC.

                                 EXHIBIT INDEX

                                        
Regulation S-K                   Document
--------------                   --------
   Exhibit                        
   -------

    4.1        Certificate of Incorporation, as amended.
               Incorporated by reference to the OEC Medical Systems,
               Inc. Form 10-K, filed March 30, 1994.

    4.2        Restated By-Laws, as amended May 15, 1997.
               Incorporated by reference to the OEC Medical Systems,
               Inc. Form 10-Q, filed August 8, 1997.

    4.3        OEC Medical Systems, Inc. 1998 Stock Option Plan.

    4.4        OEC Medical Systems, Inc. 1993 Employee Incentive
               Stock Acquisition Plan, as amended and restated.

    4.5        Rights Agreement, dated as of June 20, 1988, between
               Diasonics, Inc. and Bank of America NT&SA.
               Incorporated by reference to Exhibit 4.3 of the
               Diasonics, Inc. Form 8-K, filed August 1, 1988.

    4.6        Diasonics, Inc. 1979 Stock Option Plan, amended and
               restated as of June 1, 1982. Incorporated by
               reference to Exhibit 10.6 of the Diasonics, Inc.
               Registration Statement on Form S-8, filed May 2, 1983.

    4.7        OEC Medical Systems, Inc. 1990 Stock Option/Stock
               Purchase Plan.  Incorporated by reference to 
               Exhibit 99.1 of the Diasonics, Inc.  Form S-8, filed
               on September 30, 1993 (the "1993 S-8").

    4.8        Warrant for the Purchase of Common Shares issued to
               PaineWebber R&D Partners II, L.P., as amended.
               Incorporated by reference to the OEC Medical Systems,
               Inc. Form 10-K, filed on March 30, 1994.

    4.9        Form of Option Agreement used in connection with
               non-qualified options having service-vesting
               provisions granted under the Discretionary Option
               Grant Program.

    4.10       Form of Option Agreement used in connection with
               non-qualified options having milestone vesting
               provisions granted under the 

                                       10
Discretionary Option Grant Program.

              4.11      Form of Option Agreement used in connection with
                        incentive stock options.

              4.12      Form of Option Agreement used in connection with
                        options granted under the Automatic Option Grant
                        Program.

              4.13      Note and Stock Pledge Agreement between Ruediger
                        Naumann-Etienne and OEC Medical Systems, Inc., dated
                        September 5, 1995. Incorporated by reference to the
                        OEC Medical Systems, Inc. Form 10-K, filed April 1,
                        1996.

              4.14      Form of Warrant Agreement used in connection with
                        grant to independent contractors for the purchase of
                        common shares. Incorporated by reference to the OEC
                        Medical Systems, Inc. Form 10-K, filed March 27, 1997.

              4.15      Agreement dated December 17, 1996, to acquire full
                        ownership of Barwig Medizinische Systeme GmbH (BMS).
                        Incorporated by reference to the OEC Medical Systems,
                        Inc. Form 10-K, filed March 27, 1997.

              4.16      Form of Incentive Stock Option Agreement-Initial Grant
                        to be generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan, Incorporated by reference to
                        Exhibit 99.2 of the 1993 S-8.

              4.17      Form of Incentive Stock Option Agreement to be generally
                        used in connection with the 1990 Stock Option/Stock
                        Purchase Plan. Incorporated by reference to Exhibit 99.3
                        of the 1993 S-8.

              4.18      Form of Non-Qualified Stock Option Agreement-Initial
                        Grant to be generally used in connection with the 1990
                        Stock Option/Stock Purchase Plan. Incorporated by
                        reference to Exhibit 99.4 of the 1993 S-8.

              4.19      Form of Non-Qualified Stock Option Agreement to be
                        generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan. Incorporated by reference to
                        Exhibit 99.5 of the 1993 S-8.

              4.20      Form of Stock Option Agreement (Non-Employee Director)
                        to be generally used in connection with the automatic
                        option grant program of the 1990 Stock Option/Stock
                        Purchase Plan. Incorporated by reference to Exhibit 99.6
                        of the 1993 S-8.

              4.21      Form of Stock Option Agreement-Direct Stock Purchase to
                        be generally used in connection with the 1990 Stock
                        Option/Stock Purchase Plan. Incorporated by reference to
                        Exhibit 99.7 of the 1993 S-8.

              4.22      Form of Stock Option Adjustment Agreement used in
                        connection with the 1990 Stock Option/Stock Purchase
                        Agreement. Incorporated by reference to Exhibit 99.8 of
                        the 1993 S-8.

              5         Opinion of Holland & Hart LLP, as to the legality of
                        securities being registered.

              23.1      Consent of Deloitte & Touche LLP,  Independent
                        Auditor.

              23.2      Consent of Holland & Hart LLP (contained in 
                        Exhibit 5).

              24        Power of Attorney (included on page 8 of this
                        Registration Statement).

         -----------------

                                       11