Prospectus

                           IONICS, INCORPORATED

                     1,037,669 Shares of Common Stock

                              ($1 par value)

THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES
AND EXCHANGE COMMISSION NOR HAS THE COMMISSION PASSED UPON THE ACCURACY OR
ADEQUACY OF THIS PROSPECTUS.  ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

     This Prospectus relates to the offer and sale by the Selling
Stockholders for their respective accounts of up to 1,037,669 shares of the
Common Stock, $1.00 par value, of Ionics, Incorporated (the "Company"),
representing all shares which have been or may be purchased prior to June
30, 1999 by the Selling Stockholders upon exercise of stock options granted
by the Company under its 1955 Employee Stock Option Plan, its 1965 and 1975
Qualified Stock Option Plans, its 1973 and 1979 Stock Option Plans and upon
exercise of certain non-qualified options granted in 1951.  A total of
405,420 shares have already been purchased pursuant to such Plans and are
now owned by the Selling Stockholders, and 670,500 shares are subject to
outstanding options held by the Selling Stockholders which are exercisable
at any time prior to June 30, 1999.  As the result of a dividend declared
December 22, 1987, and pursuant to the terms of a Renewed Rights Agreement
dated as of August 19, 1997, upon exercise of an option the optionee will
receive, together with each share of Common Stock, a Right to purchase one
share of Common Stock of the Company.  The terms and conditions of such
Rights are described in the report filed by the Company on Form 8-K dated
August 27, 1997.

     This Prospectus also covers such additional shares as the foregoing
may be converted into by reason of any stock dividend, split of shares,
recapitalization or other changes in the Common Stock of the Company.
Specific information as to the Selling Stockholders may be found on pages 3
through 5 of this Prospectus.

     The shares of Common Stock covered by this Prospectus may be offered
or sold from time to time by the Selling Stockholders on the New York Stock
Exchange, over-the-counter, or privately, at prices prevailing at the time
for the Company's Common Stock.  Any broker or dealer involved in the offer
or sale of the shares may receive an ordinary brokerage commission or
discount.  The Company will not receive any of the proceeds from sales by
Selling Stockholders.

     The Common Stock of the Company is traded on the New York Stock
Exchange.  On June 29, 1998, the last sales price as reported by such
exchange was $37 3/8.
                       ____________________________

               The date of this Prospectus is June 30, 1998




                                    -2-



Available Information

     Ionics, Incorporated (the "Company") is subject to the informational
requirements of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), and in accordance therewith files reports and other
information with the Securities and Exchange Commission (the "Commission").

     Reports and proxy statements and other information filed by the
Company can be inspected and copied at the public reference facilities
maintained by the Commission at 450 Fifth Street, N.W., Room 1024,
Washington, D.C. 20549.  Copies of such material can be obtained from the
Public Reference Section of the Commission at the above address at
prescribed rates.  Such material can also be obtained from the following
regional offices of the Commission:  New York Regional office, 75 Park
Plaza, New York, New York  10007; and Chicago Regional office, 219 South
Dearborn Street, Chicago, Illinois 60604.

     The Company's Common Stock is listed on the New York Stock Exchange,
and reports, proxy statements and other information concerning the Company
can also be inspected at the Exchange.  Additional updating information
with respect to the securities covered herein may be provided in the future
by means of appendices or supplements to this Prospectus.

     The Company will provide without charge to each person to whom this
Prospectus is delivered, upon written or oral request of such person, a
copy of any and all of the information that has been incorporated by
reference in the Registration Statement of which this Prospectus forms a
part but not delivered with the Prospectus.  Such requests should be made
to Ionics, Incorporated, 65 Grove Street, Watertown, Massachusetts 02472,
Attention, Clerk; telephone number:  (617) 926-2500.

     No dealer, salesman or other person has been authorized to give any
information or to make any representations not contained in this Prospectus
in connection with the offering made by the Prospectus and if given or
made, such information or representations must not be relied upon as having
been authorized by the Company or by the Selling Stockholders.  This
Prospectus does not constitute an offering in any state or other
jurisdiction in which such offering may not lawfully be made.  Neither the
delivery of this Prospectus nor any sale made hereunder shall, under any
circumstances, create any implication that there has been no change in the
affairs of the Company since the date hereof.




                                    -3-




Table of Contents
                                                        Page
Identity of Issuer.......................................3
Plan of Distribution.....................................3
Selling Stockholders.....................................3
Documents Incorporated by Reference......................5
Further Information......................................5

Identity of Issuer

     The issuer of the securities included herein is Ionics, Incorporated,
whose principal executive offices are located at 65 Grove Street,
Watertown, Massachusetts 02472.  The Company's telephone number is (617)
926-2500.

Plan of Distribution

     The shares of Common Stock covered by this Prospectus may be offered
or sold from time to time by the Selling Stockholders on the New York Stock
Exchange, over-the-counter or privately.  Such sales will be made at prices
prevailing at the time for the Company's Common Stock.  The Company will
not receive any of the proceeds from sales by Selling Stockholders.

     Any broker or dealer involved in the offer or sale of the shares
included herein may receive an ordinary brokerage commission or discount.
To the knowledge of the Company, there is currently no agreement with any
broker or dealer respecting such transactions.  Upon sale of such shares,
any or all of the Selling Stockholders or anyone effecting sales on behalf
of the Selling Stockholders may be deemed an underwriter, as that term is
defined in the Securities Act of 1933, as amended; neither the Company nor
any of the Selling Stockholders so concede.  All expenses of the
registration of the shares covered by this Prospectus are to be borne by
the Company.

Selling Stockholders

     Information is provided below on each Selling Stockholder, as to his
relationship with the Company during the last three years, the number of
Shares of Common Stock owned beneficially by him as of June 30, 1998, the
number of shares he may acquire before June 30, 1999 by the exercise of
options already granted to him under the stock option plans referred to
herein, and the number of shares which each Selling Stockholder presently
anticipates selling under this Prospectus.  Shares held by Selling
Stockholders may be sold either pursuant to the Registration Statement of
which this Prospectus is a part or pursuant to Rule 144 under the
Securities Act of 1933, as amended.




                                    -4-



                  Outstanding Shares Owned      Shares      Shares
Name, Address     Beneficially on June 30, 1998 Being       to be
and Relationship  and Shares Subject            Offered     Owned if
to the Company    to Outstanding Options        for Sale    All Shares
During Past       Exercisable Before            under this  in Column
Three Years       June 30, 1999 (1)(2)          Prospectus  3 Are Sold 
                                                   
Arthur L.         
Goldstein             636,927 (3)(4)            50,000      586,927 (5)
 65 Grove St.
 Watertown, MA
 Chairman of the
 Board, President
 and Chief
 Executive Officer

William E.
Katz                  249,204 (4)               50,000      199,204 (5)
 65 Grove St.
 Watertown, MA
 Executive
 Vice President
 and Director

Theodore G.
Papastavros           151,883 (3)               25,000      126,883 (5)
 65 Grove St.
 Watertown, MA
 Vice President
(and Treasurer until
 November 14, 1997) 


(1)  If options which are exercisable before June 30, 1999 are exercised,
certain of the shares would be subject to repurchase by the Company in
varying amounts if the individual's employment by the Company were to
terminate before specified dates.

(2)  Assumes that all options exercisable before June 30, 1999 will be
exercised by the Selling Stockholder.

(3)  Includes beneficial ownership of certain shares held in the Company's
Section 401(k) Stock Savings Plan for the account of this individual
(401(k) data as of June 23, 1998).

(4)  Does not include 6,400 and 8,400 shares owned by members of the
immediate families of Messrs. Goldstein and Katz, respectively; beneficial
ownership of these shares is disclaimed.  




                                    -5-




(5)  In the event all options are exercised and shares registered hereunder
are sold, Messrs. Goldstein and Katz would hold 3.6% and 1.2%,
respectively, and Mr. Papastavros would hold less than 1% of the Company's
outstanding shares.



Documents Incorporated by Reference

     The following documents are incorporated in this Prospectus by
reference:  (i) the Annual Report of the Company filed on Form 10-K
pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 for
the year ended December 31, 1997, containing consolidated balance sheets of
the Company at December 31, 1997 and 1996 and the related consolidated
statements of income, stockholders' equity and cash flows for the three
years ended December 31, 1997 together with the related notes and the
report thereon dated February 17, 1998 of Coopers & Lybrand L.L.P.,
independent accountants; (ii) the Quarterly Report of the Company on Form
10-Q for the fiscal quarter ended March 31, 1998; and (iii) the description
of the Common Stock of the Company contained in the Registration Statement
of the Company filed on Form 8-A pursuant to Section 12 of the Securities
Exchange Act of 1934 filed with the Commission on September 27, 1990.  All
documents hereafter filed by the Company pursuant to Sections 13(a), 13(c),
14 or 15(d) of the Securities Exchange Act of 1934 and prior to the
termination of the offering of the securities hereunder shall be deemed to
be incorporated by reference in this Prospectus and to be a part hereof
from the date of filing of such documents.

Further Information

     Under the By-Laws of the Company, any director made a party to any
action by reason of the fact that he is or was a director or officer, or by
reason of any action alleged to have been taken or omitted by him as a
director or officer of the Company, shall be indemnified by the Company
against all costs and expenses, including reasonable attorneys' fees and
costs of settlements, reasonably incurred by him in connection with the
defense of such action, except in relation to matters as to which it shall
be finally adjudicated in any action that such individual has not acted in
good faith in the reasonable belief that his action was in the best
interests of the Company.




                                    -6-

     Moreover, the Articles of Organization provide that, a director of the
Company shall have no personal liability to the Company or to its
stockholders for monetary damages for breach of fiduciary duty as a
director, notwithstanding any provision of law imposing such liability;
provided, however, that such provision shall not eliminate or limit the
liability of a director (i) for any breach of the director's duty of
loyalty to the Company or its stockholders; (ii) for acts or omissions not
in good faith or which involve intentional misconduct or knowing violations
of law; (iii) under sections 61 or 62 of Chapter 156B of the General Laws
of Massachusetts; or (iv) for any transaction from which the director
derived an improper personal benefit.

     Officers who are not directors may be indemnified to the extent
authorized by the Board of Directors.

     Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and
controlling persons of the Company pursuant to the foregoing provision, the
Company 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 of 1933, as amended and is therefore unenforceable.