<PAGE>

     As filed with the Securities and Exchange Commission on June 6, 2000
                                                  Registration No. 333-_________
================================================================================

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549

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

                                   FORM S-8

                            REGISTRATION STATEMENT
                                     UNDER
                          THE SECURITIES ACT OF 1933

                               CYTYC CORPORATION
--------------------------------------------------------------------------------
            (Exact Name of Registrant as Specified in Its Charter)

                Delaware                                  02-0407755
--------------------------------------------------------------------------------
    (State or other jurisdiction of                  (I.R.S. Employer
    incorporation or organization)                   Identification No.)

                    85 Swanson Road, Boxborough, MA  01719
--------------------------------------------------------------------------------
              (Address of Principal Executive Offices) (Zip Code)

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

                                1995 Stock Plan
--------------------------------------------------------------------------------
                           (Full Title of the Plan)

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

                              PATRICK J. SULLIVAN
                     President and Chief Executive Officer
                               Cytyc Corporation
                                85 Swanson Road
                             Boxborough, MA  01719
                                (978) 263-8000
--------------------------------------------------------------------------------
                     (Name, Address and Telephone Number,
                  including Area code, of Agent For Service)

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

                                   Copy to:

                           JONATHAN M. MOULTON, ESQ.
                        Testa, Hurwitz & Thibeault, LLP
                               High Street Tower
                                125 High Street
                          Boston, Massachusetts 02110
                                (617) 248-7000


                        CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
================================================================================
     Title Of                             Maximum       Maximum
    Securities           Amount          Offering      Aggregate      Amount of
       To Be             To Be           Price Per      Offering    Registration
    Registered       Registered(1)       Share(2)        Price           Fee
--------------------------------------------------------------------------------
<S>              <C>                <C>              <C>           <C>
1995 STOCK PLAN
Common Stock,
$.01 par value     871,332 shares         $49.13       $42,804,185   $11,300.30
================================================================================
</TABLE>
/(1)/ Pursuant to the terms of the 1995 Stock Plan of Cytyc Corporation (the
      "Company"), an additional 871,332 shares of Common Stock may be issued
      effective as of the first trading day of 2000 and such additional shares
      are registered hereby. Upon the filing and effectiveness of this
      Registration Statement on Form S-8, the total number of shares of Common
      Stock registered pursuant to the 1995 Stock Plan will be 5,156,718 shares.

/(2)/ None of such shares are subject to outstanding options. The price of
      $49.13 per share, which is the average of the high and low prices reported
      on the Nasdaq National Market on May 31, 2000, is set forth solely for
      purposes of calculating the filing fee pursuant to Rule 457(c).
================================================================================

   In January 2000, the Company effected a two-for-one stock split in the form
of a stock dividend to holders of record of the Company's Common Stock on
January 14, 2000.  All share numbers in this Registration Statement have been
adjusted to reflect such stock split.

   This Registration Statement registers additional securities of the same class
as other securities for which the Company's Registration Statement on Form S-8
(File No. 333-2196), as filed with the Securities and Exchange Commission (the
"Commission") on March 8, 1996 relating to the Company's 1988 Stock Plan, 1989
Stock Plan, 1995 Non-Employee Director Stock Option Plan, 1995 Employee Stock
Purchase Plan and 1995 Stock Plan, the Company's Registration Statement on Form
S-8 (File No. 333-22675), as filed with the Commission on March 3, 1997 relating
to the Company's 1995 Stock Plan, the Company's Registration Statement on Form
S-8 (File No. 333-59291), as filed with the Commission on July 17, 1998 relating
to the Company's 1995 Stock Plan, and the Company's Registration Statement on
Form S-8 (File No. 333-82925), as filed with the Commission on July 15, 1999
relating to the Company's 1995 Stock Plan, are effective.  Pursuant to General
Instruction E to Form S-8, the contents of the above-listed Registration
Statements are hereby incorporated by reference.
<PAGE>

                                      -2-

                                    PART II
              INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

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

   The Company previously registered under the Securities Act an aggregate of
4,285,386 shares of Common Stock offered pursuant to the 1995 Stock Plan
pursuant to a Registration Statement on Form S-8 (File No. 333-2196) filed with
the Commission on March 8, 1996, a Registration Statement on Form S-8 (File No.
333-22675) filed with the Commission on March 3, 1997, a Registration Statement
on Form S-8 (File No. 333-59291) filed with the Commission on July 17, 1998, and
a Registration Statement on Form S-8 (File No. 333-82925) filed with the
Commission on July 15, 1999, all which are incorporated in this Registration
Statement by reference.

   The following documents filed with the Commission are incorporated by
reference in this Registration Statement:

   (a)  The Company's Annual Report on Form 10-K for the fiscal year ended
        December 31, 1999 filed pursuant to the Securities and Exchange Act of
        1934, as amended (the "Exchange Act");

   (b)  The Company's Quarterly Report on Form 10-Q for the fiscal quarter ended
        March 31, 2000 filed pursuant to the Exchange Act; and

   (c)  The section entitled "Description of Registrant's Securities to be
        Registered" contained in the Company's Registration Statement on
        Form 8-A, filed with the Commission pursuant to Section 12(g) of the
        Exchange Act on January 16, 1996.

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

   Any statement contained in any document incorporated, or deemed to be
incorporated, by reference herein shall be deemed to be modified or superseded
for purposes of this Registration Statement to the extent that a statement
contained herein or in any subsequently filed document which also is, or is
deemed to be, incorporated by reference herein modifies or supersedes such
statement.  Except as so modified or superseded, such statement shall not be
deemed to constitute a part of this Registration Statement.
<PAGE>

                                      -3-

Item 8.  Exhibits
         --------

Exhibit No.  Description of Exhibit
-----------  ----------------------
    4 (1)    1995 Stock Plan, as amended

    5 (2)    Opinion of Testa, Hurwitz & Thibeault, LLP

 23.1 (2)    Consent of Arthur Andersen LLP

 23.2 (2)    Consent of Testa, Hurwitz & Thibeault, LLP (included in Exhibit 5)

 24.1 (2)    Power of Attorney (included as part of the signature page to this
             Registration Statement)
------------
(1)  Incorporated by reference to Exhibit 4.8 of the Company's Registration
     Statement on Form S-8 (File No. 333-2196).

(2)  Filed herewith.
<PAGE>

                                      -4-

                                  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 Boxborough, Commonwealth of Massachusetts, on this
6th day of June, 2000.

                               CYTYC CORPORATION


                               By:  /s/ Patrick J. Sullivan
                                    -------------------------------------
                                    Patrick J. Sullivan
                                    President and Chief Executive Officer

                        POWER OF ATTORNEY AND SIGNATURES

   We, the undersigned officers and directors of Cytyc Corporation, hereby
severally constitute and appoint Patrick J. Sullivan and Joseph W. Kelly, and
each of them singly, our true and lawful attorneys, with full power to them and
each of them singly, to sign for us in our names in the capacities indicated
below, all pre-effective and post-effective amendments to this registration
statement, and generally to do all things in our names and on our behalf in such
capacities to enable Cytyc Corporation to comply with the provisions of the
Securities Act of 1933, as amended, and all requirements of the Securities and
Exchange Commission.

   Pursuant to the requirements of the Securities Act of 1933, as amended, this
registration statement has been signed by the following persons in the
capacities and on the date indicated.

Signature                  Capacity                                 Date
---------                  --------                                 ----

/s/ Patrick J. Sullivan    President, Chief Executive           June 6, 2000
-----------------------    Officer and Director
Patrick J. Sullivan        (Principal Executive Officer)



/s/ Joseph W. Kelly        Senior Vice President,               June 6, 2000
-----------------------    Chief Financial Officer and
Joseph W. Kelly            Treasurer
                           (Principal Financial and
                           Accounting Officer)



/s/ Sally W. Crawford      Director                             June 6, 2000
-----------------------
Sally W. Crawford


/s/ Alfred J. Battaglia    Director                             June 6, 2000
-----------------------
Alfred J. Battaglia
<PAGE>

                                      -5-

Signature                  Capacity                                 Date
---------                  --------                                 ----

/s/ William G. Little      Director                             June 6, 2000
-------------------------
William G. Little


/s/ C. William McDaniel    Director                             June 6, 2000
-------------------------
C. William McDaniel


/s/ Anna S. Richo          Director                             June 6, 2000
-------------------------
Anna S. Richo


/s/ Monroe E. Trout, M.D.  Director                             June 6, 2000
-------------------------
Monroe E. Trout, M.D.


/s/ Walter E. Boomer       Director                             June 6, 2000
-------------------------
Walter E. Boomer
<PAGE>

                                 EXHIBIT INDEX
                                 -------------

    Exhibit        Description of Exhibit
    -------        ----------------------

      4 (1)        1995 Stock Plan

      5 (2)        Opinion of Testa, Hurwitz & Thibeault, LLP

   23.1 (2)        Consent of Arthur Andersen LLP

   23.2 (2)        Consent of Testa, Hurwitz & Thibeault, LLP (included in
                   Exhibit 5)

   24.1 (2)        Power of Attorney (included as part of the signature page to
                   this Registration Statement)
--------------------
(1)  Incorporated by reference to Exhibit 4.8 of the Company's Registration
     Statement on Form S-8 (File No. 333-2196).

(2)  Filed herewith.
[{"type": "S-8", "sequence": "1", "filename": "0001.txt", "description": "FORM S-8", "secsgml_size_bytes": 12895}]
{"company-data": {"conformed-name": "CYTYC CORP", "cik": "0000849778", "assigned-sic": "3826", "irs-number": "020407755", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-38644", "film-number": "649864"}, "business-address": {"street1": "237 CEDAR HILL ST", "city": "MARLBOROUGH", "state": "MA", "zip": "01752", "phone": "5082638000"}, "mail-address": {"street1": "85 SWANSON ROAD", "city": "BOXBOROUGH", "state": "MA", "zip": "01719"}}
As filed with the Securities and Exchange Commission on June 6, 2000
                                                  Registration No. 333-_________
================================================================================

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549

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

                                   FORM S-8

                            REGISTRATION STATEMENT
                                     UNDER
                          THE SECURITIES ACT OF 1933

                               CYTYC CORPORATION
--------------------------------------------------------------------------------
            (Exact Name of Registrant as Specified in Its Charter)

                Delaware                                  02-0407755
--------------------------------------------------------------------------------
    (State or other jurisdiction of                  (I.R.S. Employer
    incorporation or organization)                   Identification No.)

                    85 Swanson Road, Boxborough, MA  01719
--------------------------------------------------------------------------------
              (Address of Principal Executive Offices) (Zip Code)

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

                                1995 Stock Plan
--------------------------------------------------------------------------------
                           (Full Title of the Plan)

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

                              PATRICK J. SULLIVAN
                     President and Chief Executive Officer
                               Cytyc Corporation
                                85 Swanson Road
                             Boxborough, MA  01719
                                (978) 263-8000
--------------------------------------------------------------------------------
                     (Name, Address and Telephone Number,
                  including Area code, of Agent For Service)

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

                                   Copy to:

                           JONATHAN M. MOULTON, ESQ.
                        Testa, Hurwitz & Thibeault, LLP
                               High Street Tower
                                125 High Street
                          Boston, Massachusetts 02110
                                (617) 248-7000

                        CALCULATION OF REGISTRATION FEE
================================================================================
     Title Of                             Maximum       Maximum
    Securities           Amount          Offering      Aggregate      Amount of
       To Be             To Be           Price Per      Offering    Registration
    Registered       Registered(1)       Share(2)        Price           Fee
--------------------------------------------------------------------------------
1995 STOCK PLAN
Common Stock,
$.01 par value     871,332 shares         $49.13       $42,804,185   $11,300.30
================================================================================
/(1)/ Pursuant to the terms of the 1995 Stock Plan of Cytyc Corporation (the
      "Company"), an additional 871,332 shares of Common Stock may be issued
      effective as of the first trading day of 2000 and such additional shares
      are registered hereby. Upon the filing and effectiveness of this
      Registration Statement on Form S-8, the total number of shares of Common
      Stock registered pursuant to the 1995 Stock Plan will be 5,156,718 shares.

/(2)/ None of such shares are subject to outstanding options. The price of
      $49.13 per share, which is the average of the high and low prices reported
      on the Nasdaq National Market on May 31, 2000, is set forth solely for
      purposes of calculating the filing fee pursuant to Rule 457(c).
================================================================================

   In January 2000, the Company effected a two-for-one stock split in the form
of a stock dividend to holders of record of the Company's Common Stock on
January 14, 2000.  All share numbers in this Registration Statement have been
adjusted to reflect such stock split.

   This Registration Statement registers additional securities of the same class
as other securities for which the Company's Registration Statement on Form S-8
(File No. 333-2196), as filed with the Securities and Exchange Commission (the
"Commission") on March 8, 1996 relating to the Company's 1988 Stock Plan, 1989
Stock Plan, 1995 Non-Employee Director Stock Option Plan, 1995 Employee Stock
Purchase Plan and 1995 Stock Plan, the Company's Registration Statement on Form
S-8 (File No. 333-22675), as filed with the Commission on March 3, 1997 relating
to the Company's 1995 Stock Plan, the Company's Registration Statement on Form
S-8 (File No. 333-59291), as filed with the Commission on July 17, 1998 relating
to the Company's 1995 Stock Plan, and the Company's Registration Statement on
Form S-8 (File No. 333-82925), as filed with the Commission on July 15, 1999
relating to the Company's 1995 Stock Plan, are effective.  Pursuant to General
Instruction E to Form S-8, the contents of the above-listed Registration
Statements are hereby incorporated by reference.
-2-

                                    PART II
              INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

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

   The Company previously registered under the Securities Act an aggregate of
4,285,386 shares of Common Stock offered pursuant to the 1995 Stock Plan
pursuant to a Registration Statement on Form S-8 (File No. 333-2196) filed with
the Commission on March 8, 1996, a Registration Statement on Form S-8 (File No.
333-22675) filed with the Commission on March 3, 1997, a Registration Statement
on Form S-8 (File No. 333-59291) filed with the Commission on July 17, 1998, and
a Registration Statement on Form S-8 (File No. 333-82925) filed with the
Commission on July 15, 1999, all which are incorporated in this Registration
Statement by reference.

   The following documents filed with the Commission are incorporated by
reference in this Registration Statement:

   (a)  The Company's Annual Report on Form 10-K for the fiscal year ended
        December 31, 1999 filed pursuant to the Securities and Exchange Act of
        1934, as amended (the "Exchange Act");

   (b)  The Company's Quarterly Report on Form 10-Q for the fiscal quarter ended
        March 31, 2000 filed pursuant to the Exchange Act; and

   (c)  The section entitled "Description of Registrant's Securities to be
        Registered" contained in the Company's Registration Statement on
        Form 8-A, filed with the Commission pursuant to Section 12(g) of the
        Exchange Act on January 16, 1996.

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

   Any statement contained in any document incorporated, or deemed to be
incorporated, by reference herein shall be deemed to be modified or superseded
for purposes of this Registration Statement to the extent that a statement
contained herein or in any subsequently filed document which also is, or is
deemed to be, incorporated by reference herein modifies or supersedes such
statement.  Except as so modified or superseded, such statement shall not be
deemed to constitute a part of this Registration Statement.
-3-

Item 8.  Exhibits
         --------

Exhibit No.  Description of Exhibit
-----------  ----------------------
    4 (1)    1995 Stock Plan, as amended

    5 (2)    Opinion of Testa, Hurwitz & Thibeault, LLP

 23.1 (2)    Consent of Arthur Andersen LLP

 23.2 (2)    Consent of Testa, Hurwitz & Thibeault, LLP (included in Exhibit 5)

 24.1 (2)    Power of Attorney (included as part of the signature page to this
             Registration Statement)
------------
(1)  Incorporated by reference to Exhibit 4.8 of the Company's Registration
     Statement on Form S-8 (File No. 333-2196).

(2)  Filed herewith.
-4-

                                  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 Boxborough, Commonwealth of Massachusetts, on this
6th day of June, 2000.

                               CYTYC CORPORATION

                               By:  /s/ Patrick J. Sullivan
                                    -------------------------------------
                                    Patrick J. Sullivan
                                    President and Chief Executive Officer

                        POWER OF ATTORNEY AND SIGNATURES

   We, the undersigned officers and directors of Cytyc Corporation, hereby
severally constitute and appoint Patrick J. Sullivan and Joseph W. Kelly, and
each of them singly, our true and lawful attorneys, with full power to them and
each of them singly, to sign for us in our names in the capacities indicated
below, all pre-effective and post-effective amendments to this registration
statement, and generally to do all things in our names and on our behalf in such
capacities to enable Cytyc Corporation to comply with the provisions of the
Securities Act of 1933, as amended, and all requirements of the Securities and
Exchange Commission.

   Pursuant to the requirements of the Securities Act of 1933, as amended, this
registration statement has been signed by the following persons in the
capacities and on the date indicated.

Signature                  Capacity                                 Date
---------                  --------                                 ----

/s/ Patrick J. Sullivan    President, Chief Executive           June 6, 2000
-----------------------    Officer and Director
Patrick J. Sullivan        (Principal Executive Officer)

/s/ Joseph W. Kelly        Senior Vice President,               June 6, 2000
-----------------------    Chief Financial Officer and
Joseph W. Kelly            Treasurer
                           (Principal Financial and
                           Accounting Officer)

/s/ Sally W. Crawford      Director                             June 6, 2000
-----------------------
Sally W. Crawford

/s/ Alfred J. Battaglia    Director                             June 6, 2000
-----------------------
Alfred J. Battaglia
-5-

Signature                  Capacity                                 Date
---------                  --------                                 ----

/s/ William G. Little      Director                             June 6, 2000
-------------------------
William G. Little

/s/ C. William McDaniel    Director                             June 6, 2000
-------------------------
C. William McDaniel

/s/ Anna S. Richo          Director                             June 6, 2000
-------------------------
Anna S. Richo

/s/ Monroe E. Trout, M.D.  Director                             June 6, 2000
-------------------------
Monroe E. Trout, M.D.

/s/ Walter E. Boomer       Director                             June 6, 2000
-------------------------
Walter E. Boomer
EXHIBIT INDEX
                                 -------------

    Exhibit        Description of Exhibit
    -------        ----------------------

      4 (1)        1995 Stock Plan

      5 (2)        Opinion of Testa, Hurwitz & Thibeault, LLP

   23.1 (2)        Consent of Arthur Andersen LLP

   23.2 (2)        Consent of Testa, Hurwitz & Thibeault, LLP (included in
                   Exhibit 5)

   24.1 (2)        Power of Attorney (included as part of the signature page to
                   this Registration Statement)
--------------------
(1)  Incorporated by reference to Exhibit 4.8 of the Company's Registration
     Statement on Form S-8 (File No. 333-2196).

(2)  Filed herewith.