U.S. SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 FORM 4 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(f) of the Investment Company Act of 1940 [_] Check box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). ________________________________________________________________________________ 1. Name and Address of Reporting Person* Papastavros Theodore G. -------------------------------------------------------------------------------- (Last) (First) (Middle) 23 Lawrence Road -------------------------------------------------------------------------------- (Street) Weston MA 02193 -------------------------------------------------------------------------------- (City) (State) (Zip) ________________________________________________________________________________ 2. Issuer Name and Ticker or Trading Symbol Ionics, Incorporated ________________________________________________________________________________ 3. IRS Identification Number of Reporting Person, if an Entity (Voluntary) ###-##-#### ________________________________________________________________________________ 4. Statement for Month/Year 12/01 ________________________________________________________________________________ 5. If Amendment, Date of Original (Month/Year) ________________________________________________________________________________ 6. Relationship of Reporting Person to Issuer (Check all applicable) [_] Director [_] 10% Owner [x] Officer (give title below) [_] Other (specify below) Vice President, Strategic Planning ________________________________________________________________________________ 7. Individual or Joint/Group Filing (Check applicable line) [x] Form filed by one Reporting Person [_] Form filed by more than one Reporting Person ________________________________________________________________________________ ================================================================================ Table I -- Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned ================================================================================

* If the Form is filed by more than one Reporting Person, see Instruction 4(b)(v). Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. (Print or Type Responses) (Over) (Form 4-07/99) FORM 4 (continued) Table II -- Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities) ================================================================================

Explanation of Responses: *Shares acquired as a result of reporting person's participation in Ionics Section 401(k) Stock Savings Plan (shares are held in the name of trustee). 401(k) data reported as of 1/14/02. /s/Theodore G. Papastavros January 17, 2002 --------------------------------------------- ----------------------- **Signature of Reporting Person Date ** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a). Note: File three copies of this Form, one of which must be manually signed. If space provided is insufficient, see Instruction 6 for procedure. Page 2 EDGARLink 7.0 (8/00) Ver. 3.1

PAPASTAVROS THEODORE G 4