<PAGE>
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES AND EXCHANGE ACT OF 1934
(AMENDMENT NO. 4)*
Brooks Automation, Inc.
- -------------------------------------------------------------------------------
(Name of Issuer)
Common Stock, $.01 Par Value
------------------------------
(Title of Class of Securities)
11434A 10 0
- -------------------------------------------------------------------------------
(CUSIP Number)
- -------------------------------------------------------------------------------
(Date of Event Which Requires Filing of this Statement)
Check the following box if a fee is being paid with this statement [_]. A fee is
not required only if the filing person: (1) has previous statement on file
reporting beneficial ownership of more than five percent of the class securities
described in Item i; and (2) has filed no amendment subsequent thereto reporting
beneficial ownership of five percent or less of such class.) (See Rule 13d-7.)
*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.
The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).
<PAGE>
- --------------------- -----------------
CUSIP NO. 003654 10 0 Page 2 of 5 Pages
- --------------------- -----------------
- -------------------------------------------------------------------------------
1 NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
Robert J. Therrien
- -------------------------------------------------------------------------------
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)
(b)
- -------------------------------------------------------------------------------
3 SEC USE ONLY
- -------------------------------------------------------------------------------
4 CITIZENSHIP OR PLACE OF ORGANIZATION
U.S.A.
- -------------------------------------------------------------------------------
5 SOLE VOTING POWER
NUMBER OF 1,299,864 shares
SHARES
BENEFICIALLY -----------------------------------------------------------
OWNED BY 6 SHARED VOTING POWER
EACH
REPORTING 0 shares
PERSON -----------------------------------------------------------
WITH 7 SOLE DISPOSITIVE POWER
1,299,864 shares
-------------------------------------------------------------
8 SHARED DISPOSITIVE POWER
0 shares
- -------------------------------------------------------------------------------
9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
1,299,864 shares
- -------------------------------------------------------------------------------
10 CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
X
- -------------------------------------------------------------------------------
11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
9.6%
- -------------------------------------------------------------------------------
12 TYPE OF REPORTING PERSON
IN
- -------------------------------------------------------------------------------
<PAGE>
- --------------------- -----------------
CUSIP NO. 003654 10 0 Page 3 of 5 Pages
- --------------------- -----------------
ITEM 1(a)
Name of Issuer: Brooks Automation, Inc.
ITEM 1(b)
Address of Issuer's Principal Executive Offices: 15 Elizabeth Drive,
Chelmsford, Massachusetts 01824
ITEM 2(a)
Name of Person Filing: Robert J. Therrien
ITEM 2(b)
Address of Principal Business Office or, if none, Residence: 15 Elizabeth
Drive, Chelmsford, Massachusetts 01824
ITEM 2(c)
Citizenship: USA
ITEM 2(d)
Title of Class of Securities: Common Stock, $.01 par value
ITEM 2(e)
CUSIP Number: 11434A 10 0
ITEM 3
Not Applicable
ITEM 4
Ownership:
(a) Amount Beneficially Owned: 1,299,864 shares, including 183,850 shares
issuable pursuant to immediately exercisable stock options. Excludes
certain shares held by certain children and grandchildren of Mr.
Therrien, as to which he disclaims beneficial ownership.
(b) Percent of Class: 9.6%
<PAGE>
- --------------------- -----------------
CUSIP NO. 003654 10 0 Page 4 of 5 Pages
- --------------------- -----------------
(c) Number of Shares as to which such person has:
(i) sole power to vote or to direct the vote: 1,299,864 shares
(ii) shared power to vote or to direct the vote: -0-
(iii) sole power to dispose or to direct the disposition of:
1,299,864 shares
(iv) shared power to dispose or to direct the disposition of: -0-
ITEM 5
Ownership of Five Percent or Less of Class: Not Applicable
ITEM 6
Ownership of More than Five Percent on Behalf of Another Person:
Not Applicable
ITEM 7
Identification and Classification of the Subsidiary Which Acquired the Security
Being Reported on By the Parent Holding Company: Not Applicable
ITEM 8
Identification and Classification of Members of the Group: Not Applicable
ITEM 9
Notice of Dissolution of Group: Not Applicable
ITEM 10
Certification: Not Applicable
<PAGE>
- --------------------- -----------------
CUSIP NO. 003654 10 0 Page 5 of 5 Pages
- --------------------- -----------------
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.
February 11, 2000
- ----------------------
Date
/s/ Robert J. Therrien
- ----------------------
Signature
Robert J. Therrien
- ----------------------
Name
