UNITED STATES

                   SECURITIES AND EXCHANGE COMMISSION

                          Washington, DC 20549

                               FORM 10-Q

        [X] QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                      SECURITIES EXCHANGE ACT OF 1934

             For the quarterly period ended: March 31, 2000

                                 or

        [ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                      SECURITIES EXCHANGE ACT OF 1934

                For the transition period from ______ to ______

                       Commission File Number: 1-7211

                            IONICS, INCORPORATED
            (Exact name of registrant as specified in its charter)

           MASSACHUSETTS                               04-2068530
(State or other jurisdiction of            (IRS Employer Identification Number)
 incorporation or organization)

           65 Grove Street
       Watertown, Massachusetts                        02472
(Address of principal executive offices)             (Zip Code)

       Registrant's telephone number, including area code: (617) 926-2500

            Former name, former address and former fiscal year,
                  if changed since last report: None

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the  preceding 12 months (or for such  shorter  period that the  registrant  was
required  to file  such  reports),  and  (2) has  been  subject  to such  filing
requirements for the past 90 days.

                           Yes    X      No
                                -------     --------

Indicate the number of shares  outstanding  of each of the  issuer's  classes of
common stock, as of the latest practicable date.

At March 31, 2000 the Company had 16,210,883  shares of Common Stock,  par value
$1 per share, outstanding.


<PAGE>


                            IONICS, INCORPORATED

                                  FORM 10-Q


                                    INDEX

                                                                      Page No.

Part I -      Financial Information

              Consolidated Statements of Operations                      2

              Consolidated Balance Sheets                                3

              Consolidated Statements of Cash Flows                      4

              Notes to Consolidated Financial Statements                 5

              Management's Discussion and Analysis of Results of         7
              Operations and Financial Condition


Part II-      Other Information                                         10

              Signatures                                                11

              Exhibit Index                                             12

              Exhibit 27 - Financial Data Schedule                      13

















<PAGE>
<TABLE>
<CAPTION>


                           PART I - FINANCIAL INFORMATION

                                 IONICS, INCORPORATED
                         CONSOLIDATED STATEMENTS OF OPERATIONS
                                      (Unaudited)
                    (Amounts in thousands, except per share amounts)

                                                                                          Three Months Ended
                                                                                              March 31,
                                                                                        ----------------------
                                                                                        2000              1999
                                                                                        ----              ----
Net revenue:
<S>                                                                                    <C>               <C>
      Equipment Business Group                                                         $ 41,356          $34,439
      Ultrapure Water Group                                                              27,746           24,533
      Consumer Water Group                                                               26,419           21,859
      Instrument Business Group                                                           7,274            6,585
                                                                                       --------          -------
                                                                                        102,795           87,416
                                                                                       --------          -------

Costs and expenses:
      Cost of sales of Equipment Business Group                                          31,405           24,715
      Cost of sales of Ultrapure Water Group                                             21,865           18,238
      Cost of sales of Consumer Water Group                                              15,701           12,283
      Cost of sales of Instrument Business Group                                          3,278            3,016
      Research and development                                                            1,821            1,868
      Selling, general and administrative                                                22,974           20,109
                                                                                       --------          -------
                                                                                         97,044           80,229
                                                                                       --------          -------
Income from operations                                                                    5,751            7,187
Interest income                                                                             267              108
Interest expense                                                                           (724)            (130)
Equity income                                                                               332              163
                                                                                       --------          -------
Income before income taxes and minority interest                                          5,626            7,328

Provision for income taxes                                                                1,913            2,382
                                                                                         ------          -------
Income before minority interest                                                           3,713            4,946
Minority interest expense                                                                   151              274
                                                                                       --------          -------
Net income                                                                             $  3,562          $ 4,672
                                                                                       ========          =======
Basic earnings per share                                                               $    .22          $   .29
                                                                                        =======          =======
Diluted earnings per share                                                             $    .22          $   .29
                                                                                        =======          =======
Shares used in basic earnings per
      share calculations                                                                 16,209           16,127
                                                                                        =======          =======

Shares used in diluted earnings per
      share calculations                                                                 16,404           16,288
                                                                                        =======          =======

The accompanying notes are an integral part of these financial statements.

</TABLE>


<PAGE>
<TABLE>
<CAPTION>


                                                         IONICS, INCORPORATED
                                                      CONSOLIDATED BALANCE SHEETS
                                                              (Unaudited)
                                             (Amounts in thousands, except share amounts)

                                                                             March 31,            December 31,
                                                                               2000                   1999
                                                                           -------------         -------------
ASSETS
Current assets:
<S>                                                                                <C>                   <C>
   Cash and cash equivalents                                                 $  16,945             $  13,169
   Short-term investments                                                          409                   195
   Notes receivable, current                                                     4,349                 5,374
   Accounts receivable                                                         127,015               120,407
   Receivables from affiliated companies                                         1,139                 1,231
   Inventories:
     Raw materials                                                              20,749                20,216
     Work in process                                                            10,439                 8,913
     Finished goods                                                              4,435                 4,751
                                                                             ---------             ---------
                                                                                35,623                33,880
   Other current assets                                                         13,502                14,816
   Deferred income taxes                                                         4,730                 4,730
                                                                                ------                ------
       Total current assets                                                    203,712               193,802
Notes receivable, long-term                                                     10,819                10,027
Investments in affiliated companies                                              9,660                10,752
Property, plant and equipment:
   Land                                                                          8,519                 8,352
   Buildings                                                                    45,440                44,858
   Machinery and equipment                                                     307,841               299,303
   Other, including furniture, fixtures and vehicles                            50,364                49,119
                                                                             ---------            ----------
                                                                               412,164               401,632
   Less accumulated depreciation                                              (179,140)             (174,382)
                                                                              --------              --------
                                                                               233,024               227,250
Other assets                                                                    63,390                59,075
                                                                            ----------            ----------
       Total assets                                                           $520,605              $500,906
                                                                              ========              ========

LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
   Notes payable and current portion of long-term debt                        $ 37,749              $ 25,514
   Accounts payable                                                             45,153                41,867
   Customer deposits                                                             3,299                 2,671
   Accrued commissions                                                           2,271                 2,362
   Accrued expenses                                                             29,097                27,061
   Taxes on income                                                                 723                     -
                                                                              ---------           ----------
       Total current liabilities                                               118,292                99,475
Long-term debt and notes payable                                                 9,554                 8,351
Deferred income taxes                                                           25,298                26,803
Other liabilities                                                                4,190                 4,425
Stockholders' equity:
   Common stock, par value $1, authorized shares: 55,000,000;
   issued: 16,210,883 in 2000 and 16,201,483 in 1999                            16,211                16,201
   Additional paid-in capital                                                  159,518               159,288
   Retained earnings                                                           202,866               199,304
   Accumulated other comprehensive income                                      (15,315)              (12,905)
   Unearned compensation                                                            (9)                  (36)
                                                                             ---------            ----------
       Total stockholders' equity                                              363,271               361,852
                                                                             ---------             ---------
       Total liabilities and stockholders' equity                             $520,605              $500,906
                                                                              ========              ========
</TABLE>

The accompanying notes are an integral part of these financial statements.



<PAGE>

<TABLE>
<CAPTION>




                                                              IONICS, INCORPORATED
                                                     CONSOLIDATED STATEMENTS OF CASH FLOWS
                                                                  (Unaudited)
                                                             (Dollars in thousands)


                                                                                   Three Months Ended
                                                                                         March 31,
                                                                                 ---------------------
                                                                                  2000            1999
                                                                                  ----            ----
Operating activities:
<S>                                                                           <C>               <C>
   Net income                                                                 $  3,562          $  4,672
   Adjustments to reconcile net income to net cash provided by
   operating activities:
     Depreciation and amortization                                               7,788             6,920
     Provision for losses on accounts and notes receivable                         724               176
     Compensation expense on restricted stock awards                                27                27
     Changes in assets and liabilities:
       Notes receivable                                                           (459)              (64)
       Accounts receivable                                                      (8,434)            1,388
       Inventories                                                              (1,977)              831
       Other current assets                                                      1,199                78
       Investments in affiliates                                                   877            (1,102)
       Accounts payable and accrued expenses                                     4,904            (9,416)
       Income taxes                                                                584               877
       Other                                                                    (1,302)           (1,704)
                                                                              --------          --------
         Net cash provided by operating activities                               7,493             2,683
                                                                              --------          --------
Investing activities:
   Additions to property, plant and equipment                                  (12,369)           (9,031)
   Disposals of property, plant and equipment                                      724               214
   Acquisitions, net of cash acquired                                           (4,250)           (8,394)
   Purchase of short-term investments                                             (214)              (45)
                                                                              --------         ---------
         Net cash used by investing activities                                 (16,109)          (17,256)
                                                                               -------           -------
Financing activities:
   Principal payments on current debt                                          (18,785)           (5,862)
   Proceeds from issuance of current debt                                       29,332             7,717
   Principal payments on long-term debt                                            (18)             (518)
   Proceeds from issuance of long-term debt                                      1,285               116
   Proceeds from stock option plans                                                242               275
                                                                              --------          --------
         Net cash provided by financing activities                              12,056             1,728
                                                                              --------          --------
Effect of exchange rate changes on cash                                            336              (440)
                                                                              --------          --------
Net change in cash and cash equivalents                                          3,776           (13,285)
Cash and cash equivalents at beginning of period                                13,169            28,770
                                                                              --------          --------
Cash and cash equivalents at end of period                                     $16,945           $15,485
                                                                               =======           =======
</TABLE>

The accompanying notes are an integral part of these financial statements.




<PAGE>


                                IONICS, INCORPORATED
                      NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

1.       Basis of Presentation:
         ---------------------

         In  the  opinion  of  the  management  of  Ionics,   Incorporated  (the
         "Company"),  all  adjustments  have  been made  that are  necessary  to
         present fairly the consolidated  financial position of the Company, the
         consolidated  results of its operations and the consolidated cash flows
         for each period presented.  The consolidated  results of operations for
         the interim  periods are not  necessarily  indicative of the results of
         operations to be expected for the full year. These financial statements
         should be read in conjunction  with the Company's 1999 Annual Report as
         filed on Form 10-K with the Securities and Exchange  Commission.  Other
         than as noted  below,  there  have been no  significant  changes in the
         information  reported  in those  Notes,  other  than  from  the  normal
         business  activities  of the  Company,  and there  have been no changes
         which would,  in the opinion of management,  have a materially  adverse
         effect  upon  the  Company.   Certain  prior  year  amounts  have  been
         reclassified to conform to the current year presentation with no impact
         on net income.

2.       Earnings per share (EPS) calculations:
         -------------------------------------
<TABLE>
<CAPTION>

              (Amounts in  thousands, except per share amounts)

                                  For the period ended March 31, 2000         For the period ended March 31, 1999
                                  -----------------------------------         -----------------------------------
                                     Net                    Per Share            Net                   Per Share
                                  Income       Shares          Amount         Income       Shares         Amount
                                  ------       ------          ------         ------       ------         ------
Basic EPS
<S>                               <C>          <C>               <C>           <C>         <C>              <C>
   Income available to
      common stockholders          $3,562       16,209            $.22         $4,672       16,127          $.29
   Effect of dilutive stock
     options                           -          195               -              -          161              -
                                  ------       ------            ----         ------       ------           ----
Diluted EPS                       $3,562       16,404            $.22         $4,672       16,288           $.29
                                  ======       ======            ====         ======       ======           ====
</TABLE>

3.       Comprehensive Income:
         --------------------

         The Company has adopted the Statement of Financial Accounting Standards
         ("SFAS") No. 130, "Reporting  Comprehensive  Income," which establishes
         standards for the reporting and display of comprehensive income and its
         components.  The table  below  sets  forth  "comprehensive  income"  as
         defined by SFAS No. 130 for the  three-month  periods  ended  March 31,
         2000 and 1999.
<TABLE>
<CAPTION>

                                                                  (Amounts in thousands)
                                                              Three Months Ended March 31,

                                                                2000                      1999
                                                                ----                      ----

<S>                                                            <C>                       <C>
         Net income                                            $3,562                    $4,672
         Other comprehensive income, net of tax:
           Translation adjustments                             (2,410)                   (2,950)
                                                               ------                    ------
         Comprehensive income                                  $1,152                    $1,722
                                                               ======                    ======
</TABLE>

<PAGE>






4.       Segment Information.
         -------------------

         In 1998, the Company adopted SFAS No. 131,  "Disclosures about Segments
         of an  Enterprise  and Related  Information."  At the end of 1998,  the
         Company  changed  from three  reportable  segments  to four  reportable
         "business group" segments corresponding to a "business group" structure
         which was put into  place in the latter  part of 1998.  As of March 31,
         2000,  no changes  have been made to the basis of  segmentation  or the
         measurement  of  profit or loss from  that  which was  reported  in the
         Company's  1999 Annual Report as filed on Form 10-K with the Securities
         and Exchange  Commission,  and there were no material  changes to total
         assets by segment.

         The following  table  summarizes  the Company's  operations by the four
         business  group  segments  and  "Corporate"   (Corporate  includes  the
         elimination of intersegment transfers).

<TABLE>
<CAPTION>
                                     Equipment     Ultrapure   Consumer     Instrument
                                      Business      Water       Water        Business
Dollars in thousands                  Group         Group       Group        Group        Corporate       Total
-----------------------------------------------------------------------------------------------------------------

2000
<S>                                         <C>            <C>                       <C>     <C>
Revenue - unaffiliated customers          $41,356      $27,746    $26,419         $7,274          -     $102,795
Inter-segment transfers                     1,582          225          -            386     (2,193)           -
Gross profit                                9,951        5,881     10,718          3,996          -       30,546


1999

Revenue - unaffiliated customers          $34,439      $24,533    $21,859         $6,585          -     $ 87,416
Inter-segment transfers                       319          197          -            194       (710)           -
Gross profit                                9,724        6,295      9,576          3,569          -       29,164


</TABLE>


<PAGE>


                  MANAGEMENT'S DISCUSSION AND ANALYSIS OF
               RESULTS OF OPERATIONS AND FINANCIAL CONDITION

Results of Operations

Comparison of the Three Months Ended March 31, 2000 with the Three Months Ended
March 31, 1999
-------------------------------------------------------------------------------

Revenues for the first quarter of 2000 increased 17.6%, and net income decreased
by 23.8% compared to the results of the first quarter of 1999.  Gross Profit was
$30.5  million in the first  quarter of 2000  compared  to $29.2  million in the
first  quarter of 1999.  Gross profit  increased  in the first  quarter of 2000,
compared to the first  quarter of 1999 for the Equipment  Business  Group (EBG),
Consumer  Water Group (CWG),  and the  Instrument  Business  Group (IBG).  These
increases  were  primarily  due to higher sales volume of capital  equipment and
consumer water products. The increases were offset by a decrease in gross profit
for the Ultrapure Water Group (UWG) in the first quarter of 2000 compared to the
first quarter of 1999.  This  decrease was  primarily due to highly  competitive
pricing  pressures  in several  markets,  particularly  in the  microelectronics
industry.

Total  revenues  were $102.8  million in the first quarter of 2000 compared with
$87.4  million in the first  quarter of 1999.  Revenues for the first quarter of
2000 were higher in all of the business group segments.

EBG revenues  increased by 20.1% in the first quarter of 2000 as compared to the
first  quarter  of 1999.  This  increase  came  primarily  from  higher  capital
equipment  sales and  continuing  work on a contract  to  manufacture  a storage
system to manage the containment of spent nuclear fuels.

The revenues of the UWG  increased by $3.2 million in the first  quarter of 2000
compared to the first  quarter of 1999.  This  increase was due  primarily  from
higher sales to the microelectronics and power industries.

The 20.9%  increase in the CWG revenues  from the first quarter of 2000 compared
to the first  quarter of 1999 was due to growth in both  bottled  water and home
water  products.  Included  in the  growth  of the  home  water  business  was a
significant  increase in sales through the Company's Irish subsidiary  opened in
mid-1999.

IBG revenues  increased by $0.7 million in the first quarter of 2000 compared to
the first quarter of 1999. This increase  resulted from sales of TOC instruments
due to new European pharmaceutical regulations.

Cost of sales as a percentage of revenues was 70.3% in the first quarter of 2000
compared to 66.6% in the first quarter of 1999.

Cost of sales as a  percentage  of revenues  increased  in the first  quarter of
2000,  compared to the first quarter of 1999,  for EBG, UWG and CWG,  while such
percentage  decreased  slightly  for IBG.  The  increase  in EBG's  cost of sale
percentage to 75.9% in the first quarter of 2000 from 71.8% in the first quarter
of 1999  primarily  reflected a shift in the mix of  contracts  to lower  margin
equipment business.  Cost of sales as a percentage of revenues for UWG increased
in the first  quarter of 2000 to 78.8% from 74.3% in the first  quarter of 1999.
This  increase  resulted  from  the  continued  competitive  environment  in the
microelectronics industry for ultrapure water capital equipment. The increase in
the CWG's cost of sales to 59.4% from  56.2% is  primarily  the result of higher
distribution  costs due to increases in fuel and labor  costs.  These  increases
were offset by a slight  decrease in cost of sales for IBG in the first  quarter
of 2000,  compared to the first quarter of 1999, because of a more favorable mix
of sales.
<PAGE>


Operating  expenses as a percentage  of revenues were 24.1% in the first quarter
of 2000 and  25.1% in the first  quarter  of 1999.  The  decrease  in  operating
expenses as a percentage of revenues  primarily  reflected higher revenue growth
in EBG and UWG which  generally  have lower selling  costs  relative to revenues
than do the other business groups.

Interest income of $0.3 million for the first quarter of 2000 increased slightly
from  interest  income of $0.1 million for the first  quarter of 1999.  Interest
expense of $0.7  million for the first  quarter of 2000 was higher from the $0.1
million for the first  quarter of 1999 due to higher  average  borrowings by the
Company.

Financial Condition
-------------------

Working  capital  decreased  $8.9 million  during the first three months of 2000
while the Company's  current ratio  decreased  slightly to 1.7 at March 31, 2000
from 2.0 at December 31, 1999.  Cash provided  from net income and  depreciation
totaled $11.4 million  during the first three months of 2000,  while the primary
uses of cash  were for  additions  to  property,  plant  and  equipment  and for
acquisitions. Significant capital expenditures were generally made to expand the
Company's  bottled water  operations  and for "own and operate"  facilities.  At
March 31, 2000 notes payable and the current portion of long-term debt increased
by $12.2 million. The Company believes that its cash and cash equivalents,  cash
from operations, lines of credit and foreign exchange facilities are adequate to
meet its currently anticipated needs.

Significant  expenditures  for the  remainder  of Year 2000 are  anticipated  to
include investments in additional "own and operate" facilities and the continued
expansion of bottled water operations.

At March 31,  2000 the Company had  incurred  approximately  $3 million in costs
relating  primarily to providing  assistance  to a project  company in obtaining
financing  for,  and project  management  and design  work on, a major  seawater
desalination  project in Trinidad announced in September of 1999.  Financing for
the project has not yet been obtained.  Should financing not be obtained,  these
costs would be expensed. The Company anticipates that a determination  regarding
financing  will  occur in the  second  quarter of 2000.  The  Company  may incur
additional expenditures related to this project prior to such determination.

Accounting Pronouncements
-------------------------

In  December  1999,  the  Securities  and  Exchange  Commission  released  Staff
Accounting Bulletin ("SAB") No. 101, Revenue Recognition in Financial Statements
which was amended by SAB 101A,  delaying the  implementation  date of SAB 101 to
the second fiscal  quarter of fiscal years  beginning  after  December 15, 1999.
This  bulletin  summarizes  certain  views of the  staff on  applying  generally
accepted accounting  principles to revenue recognition in financial  statements.
The staff believes that revenue is realized or realizable and earned when all of
the following criteria are met:  persuasive  evidence of an arrangement  exists;
delivery has occurred or services have been rendered;  the seller's price to the
buyer is fixed or determinable;  and collectibility is reasonably  assured.  The
Company believes that its current revenue  recognition  policy complies with the
Commission's guidelines.




<PAGE>


Year 2000 (Y2K) Disclosure
--------------------------

The Company  undertook a program in years 1998 and 1999 to assure the ability of
its  information  and  manufacturing  systems to properly  recognize and process
date-sensitive  information  beginning on January 1, 2000. To date,  the Company
has  completed  the  transition  from  calendar  1999 to 2000  with no  reported
significant  impact to  operations.  The  company  will  continue to monitor Y2K
related  matters at suppliers and customers,  as well as the Company's  systems,
facilities  and  products,  to  ensure  that  latent  defects  do  not  manifest
themselves over the next several months.

Quantitative and Qualitative Disclosures about Market Risk
----------------------------------------------------------

Derivative Instruments and Market Risk

There has been no material change in the  information  reported in the Company's
1999  Annual  Report  as filed on Form  10-K with the  Securities  and  Exchange
Commission with respect to these risk matters.

Forward-Looking Information
---------------------------

Safe Harbor Statement under Private Securities Litigation Reform Act of 1995

The Company's future results of operations and certain  statements  contained in
this  report,  including,  without  limitation,   "Management's  Discussion  and
Analysis  of  Results  of  Operations  and  Financial   Condition,"   constitute
forward-looking  statements.  Such statements are based on management's  current
views and  assumptions and involve risks,  uncertainties  and other factors that
could  cause  actual  results to differ  materially  from  management's  current
expectations.  Among these  factors are  acceptance  of new  products  and price
pressures;  risk of nonpayment of accounts  receivable;  risks  associated  with
foreign operations;  risks of latent Y2K defects;  risks involved in litigation;
regulations and laws affecting business in each of the Company's markets; market
risk factors,  and other risks and uncertainties  described from time to time in
the Company's filings with the Securities and Exchange Commission.




<PAGE>


                               PART II - OTHER INFORMATION


Item 6.  Exhibits and Reports on Form 8-K
-------  --------------------------------

(a)        Exhibits

           3(ii)  By-Laws of the Company as amended through May 2, 2000.

(b)        Reports on Form 8-K

           No reports on Form 8-K were filed with the  Securities  and  Exchange
           Commission during the quarter ended March 31, 2000.

           All  other  items  reportable  under  Part II have  been  omitted  as
           inapplicable  or because  the  answer is  negative,  or  because  the
           information  was  previously  reported to the Securities and Exchange
           Commission.



<PAGE>


                                  SIGNATURES

           Pursuant to the requirements of the Securities  Exchange Act of 1934,
the  registrant  has duly  caused  this report to be signed on its behalf by the
undersigned thereunto duly authorized.

                                            IONICS, INCORPORATED



Date:   May 12, 2000                  By: /s/Arthur L. Goldstein
      --------------                      ----------------------------------
                                          Arthur L. Goldstein
                                          Chairman and Chief Executive Officer
                                          (duly authorized officer)



Date:   May 12, 2000                  By: /s/Robert J. Halliday
      --------------                      ----------------------------------
                                          Robert J. Halliday
                                          Executive Vice President,
                                          Chief Operating Officer and
                                          Chief Financial Officer





<PAGE>


                             EXHIBIT INDEX





                                                              Sequentially
                                                              Numbered
                                                              Page
                                                              --------------

Exhibit

3(ii)               By-Laws as amended through May 2, 2000

27.0                Financial Data Schedule                        13
                                                  (for electronic purposes only)