<PAGE>

     As filed with the Securities and Exchange Commission on April 18, 2001
                                                  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             Price                Fee
-------------------------------------------------------------------------------------------------------------------
<S>                                    <C>               <C>            <C>                 <C>
1995 STOCK PLAN                          6,450  (2)       $15.7500      $   101,587.50         $    25.40
Common Stock (par value $.01 per        25,200  (2)       $17.5630      $   442,587.60         $   110.65
share)                                  15,000  (2)       $17.5630      $   263,445.00         $    65.86
                                        60,450  (2)       $18.6880      $ 1,129,689.60         $   282.42
                                         4,300  (2)       $19.3750      $    83,312.50         $    20.83
                                        10,500  (2)       $20.0000      $   210,000.00         $    52.50
                                         3,000  (2)       $20.9583      $    62,874.90         $    15.72
                                         9,600  (2)       $20.4583      $   196,399.68         $    49.10
                                         6,000  (2)       $19.8127      $   118,876.20         $    29.72
                                         6,000  (2)       $19.4167      $   116,500.20         $    29.13
                                         6,000  (2)       $18.7553      $   112,531.80         $    28.13
                                        12,000  (2)       $19.7710      $   237,252.00         $    59.31
                                         9,000  (2)       $20.1043      $   180,938.70         $    45.23
                                         3,000  (2)       $21.3960      $    64,188.00         $    16.05
                                     1,691,484  (2)       $21.9167      $37,071,747.38         $ 9,267.94
                                     3,305,758  (3)       $16.9950      $56,181,357.21         $14,045.34

TOTAL                                5,173,742                          $96,573,288.27         $ 24,143.33
===================================================================================================================
</TABLE>
/(1)/ Pursuant to the terms of the 1995 Stock Plan of Cytyc Corporation (the
      "Company"), an additional 5,173,742 shares of Common Stock may be issued
      effective as of the first trading day of 2001 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 20,643,896
      shares.

/(2)/ Such shares are issuable upon exercise of outstanding options with fixed
      exercise prices. Pursuant to Rule 457(h), the aggregate offering price and
      the fee have been computed upon the basis of the price at which the
      options may be exercised. The offering price per share set forth for such
      shares is the exercise price per share at which such options are
      exercisable.

/(3)/ None of such shares are subject to outstanding options. The exercise price
      of such options shall be determined at the time of grant. Accordingly,
      pursuant to Rule 457(c) and Rule 457(h), the proposed maximum offering
      price of $16.9950 per share, which is the average of the high and low
      prices of the Common Stock of the Company reported on the Nasdaq National
      Market on April 16, 2001, is set forth solely for purposes of calculating
      the filing fee.
================================================================================

   In March 2001, the Company effected a three-for-one stock split in the form
of a stock dividend to holders of record of the Company's Common Stock on
February 16, 2001.  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, 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, and the Company's Registration
Statement on Form S-8 (File No. 333-38644), as filed with the Commission on June
6, 2000 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
15,470,154 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,
a Registration Statement on Form S-8 (File No. 333-82925) filed with the
Commission on July 15, 1999, and a Registration Statement on Form S-8 (File No.
333-38644) filed with the Commission on June 6, 2000, all of 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, 2000 filed pursuant to the Securities and Exchange Act of
        1934, as amended (the "Exchange Act"); and

   (b)  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
18th day of April, 2001.

                               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 Robert L. Bowen, 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         April 18, 2001
-----------------------    Officer and Vice Chairman
Patrick J. Sullivan        of the Board (Principal
                           Executive Officer)


/s/ Robert L. Bowen        Vice President,                    April 18, 2001
-----------------------    Chief Financial Officer and
Robert L. Bowen            Treasurer (Principal Financial
                           and Accounting Officer)


/s/ Sally W. Crawford      Director                           April 18, 2001
-----------------------
Sally W. Crawford


/s/ Alfred J. Battaglia    Director                           April 18, 2001
-----------------------
Alfred J. Battaglia

<PAGE>

                                      -5-

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

/s/ William G. Little      Director                           April 18, 2001
-------------------------
William G. Little


/s/ C. William McDaniel    Vice Chairman of the Board         April 18, 2001
-------------------------
C. William McDaniel


/s/ Anna S. Richo          Director                           April 18, 2001
-------------------------
Anna S. Richo


/s/ Monroe E. Trout, M.D.  Chairman of the Board              April 18, 2001
-------------------------
Monroe E. Trout, M.D.


/s/ Walter E. Boomer       Director                           April 18, 2001
-------------------------
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": 15567}]
{"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": "333-59172", "film-number": "1605866"}, "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 April 18, 2001
                                                  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             Price                Fee
-------------------------------------------------------------------------------------------------------------------
1995 STOCK PLAN                          6,450  (2)       $15.7500      $   101,587.50         $    25.40
Common Stock (par value $.01 per        25,200  (2)       $17.5630      $   442,587.60         $   110.65
share)                                  15,000  (2)       $17.5630      $   263,445.00         $    65.86
                                        60,450  (2)       $18.6880      $ 1,129,689.60         $   282.42
                                         4,300  (2)       $19.3750      $    83,312.50         $    20.83
                                        10,500  (2)       $20.0000      $   210,000.00         $    52.50
                                         3,000  (2)       $20.9583      $    62,874.90         $    15.72
                                         9,600  (2)       $20.4583      $   196,399.68         $    49.10
                                         6,000  (2)       $19.8127      $   118,876.20         $    29.72
                                         6,000  (2)       $19.4167      $   116,500.20         $    29.13
                                         6,000  (2)       $18.7553      $   112,531.80         $    28.13
                                        12,000  (2)       $19.7710      $   237,252.00         $    59.31
                                         9,000  (2)       $20.1043      $   180,938.70         $    45.23
                                         3,000  (2)       $21.3960      $    64,188.00         $    16.05
                                     1,691,484  (2)       $21.9167      $37,071,747.38         $ 9,267.94
                                     3,305,758  (3)       $16.9950      $56,181,357.21         $14,045.34

TOTAL                                5,173,742                          $96,573,288.27         $ 24,143.33
===================================================================================================================
/(1)/ Pursuant to the terms of the 1995 Stock Plan of Cytyc Corporation (the
      "Company"), an additional 5,173,742 shares of Common Stock may be issued
      effective as of the first trading day of 2001 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 20,643,896
      shares.

/(2)/ Such shares are issuable upon exercise of outstanding options with fixed
      exercise prices. Pursuant to Rule 457(h), the aggregate offering price and
      the fee have been computed upon the basis of the price at which the
      options may be exercised. The offering price per share set forth for such
      shares is the exercise price per share at which such options are
      exercisable.

/(3)/ None of such shares are subject to outstanding options. The exercise price
      of such options shall be determined at the time of grant. Accordingly,
      pursuant to Rule 457(c) and Rule 457(h), the proposed maximum offering
      price of $16.9950 per share, which is the average of the high and low
      prices of the Common Stock of the Company reported on the Nasdaq National
      Market on April 16, 2001, is set forth solely for purposes of calculating
      the filing fee.
================================================================================

   In March 2001, the Company effected a three-for-one stock split in the form
of a stock dividend to holders of record of the Company's Common Stock on
February 16, 2001.  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, 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, and the Company's Registration
Statement on Form S-8 (File No. 333-38644), as filed with the Commission on June
6, 2000 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
15,470,154 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,
a Registration Statement on Form S-8 (File No. 333-82925) filed with the
Commission on July 15, 1999, and a Registration Statement on Form S-8 (File No.
333-38644) filed with the Commission on June 6, 2000, all of 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, 2000 filed pursuant to the Securities and Exchange Act of
        1934, as amended (the "Exchange Act"); and

   (b)  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
18th day of April, 2001.

                               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 Robert L. Bowen, 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         April 18, 2001
-----------------------    Officer and Vice Chairman
Patrick J. Sullivan        of the Board (Principal
                           Executive Officer)

/s/ Robert L. Bowen        Vice President,                    April 18, 2001
-----------------------    Chief Financial Officer and
Robert L. Bowen            Treasurer (Principal Financial
                           and Accounting Officer)

/s/ Sally W. Crawford      Director                           April 18, 2001
-----------------------
Sally W. Crawford

/s/ Alfred J. Battaglia    Director                           April 18, 2001
-----------------------
Alfred J. Battaglia
-5-

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

/s/ William G. Little      Director                           April 18, 2001
-------------------------
William G. Little

/s/ C. William McDaniel    Vice Chairman of the Board         April 18, 2001
-------------------------
C. William McDaniel

/s/ Anna S. Richo          Director                           April 18, 2001
-------------------------
Anna S. Richo

/s/ Monroe E. Trout, M.D.  Chairman of the Board              April 18, 2001
-------------------------
Monroe E. Trout, M.D.

/s/ Walter E. Boomer       Director                           April 18, 2001
-------------------------
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.