<PAGE>

                                     FORM 10-K
                         SECURITIES AND EXCHANGE COMMISSION
                               WASHINGTON, D.C. 20549
/X/   ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
ACT OF 1934
                       FOR THE FISCAL YEAR ENDED APRIL 30, 1998
                                          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: 0-3947
                                    HACH COMPANY
                (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
Delaware                                                    42-0704420
(STATE OR OTHER JURISDICTION OF                        (I.R.S. EMPLOYER
INCORPORATION OR ORGANIZATION)                         IDENTIFICATION NO.)

                     5600 Lindbergh Drive, Loveland, CO  80538
                (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)  (ZIP CODE)
                                   (970) 669-3050
                (REGISTRANT'S TELEPHONE NUMBER INCLUDING AREA CODE)

Securities registered pursuant to Section 12(b) of the Act:  None
Securities registered pursuant to section 12(g) of the Act: 
                           COMMON STOCK, $1.00 PAR VALUE
                                  (TITLE OF CLASS)
                       CLASS A COMMON STOCK, $1.00 PAR VALUE
                                  (TITLE OF CLASS)

               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 by check mark if disclosure of delinquent filers 
pursuant to Item 405 of Regulation S-K is not contained herein, and will not 
be contained, to the best of registrant's knowledge, in definitive proxy or 
information statements incorporated by reference in Part III of this Form 
10-K or any amendment to this Form 10-K. _____

               As of July 10, 1998, 8,963,059 shares of Common Stock and 
8,542,581 shares of Class A Common Stock were outstanding.  The aggregate 
value of 2,689,861 shares of Common Stock and 2,735,410 shares of Class A 
Common Stock held by non-affiliates (based upon the last sales prices of 
$11.25 and $10.25 on July 10, 1998, for the Registrant's Common Stock and 
Class A Common Stock, respectively, as listed in the WALL STREET JOURNAL in 
the NASDAQ National Market System section on July 10, 1998) was approximately 
$58,000,000.

                        DOCUMENTS INCORPORATED BY REFERENCE

               Portions of the Hach Company Annual Report to Stockholders for 
the year ended April 30, 1998 (the "1998 Annual Report") are incorporated by 
reference into Parts I, II and IV.

               Portions of the Hach Company Proxy Statement for the Annual 
Meeting of Stockholders scheduled to be held September 15, 1998 (the "1998 
Proxy Statement") are incorporated by reference into Part III.

<PAGE>

                        NOTE ON FORWARD-LOOKING INFORMATION

               Certain statements contained in this Form 10-K constitute 
"forward-looking statements" within the meaning of Section 27A of the 
Securities Act of 1933 and Section 21E of the Securities Exchange Act of 
1934.  The Company intends that such forward-looking statements be subject to 
the safe harbors created thereby. Statements containing the words and phrases 
"looking ahead," "projected," "we are confident," "should be," "will be," 
"predicted," "believe," "plans," "expect," "estimated" and "anticipate" and 
similar expressions identify forward-looking statements.  These 
forward-looking statements reflect the Company's current views with respect 
to future events and financial performance, but are subject to many 
uncertainties and factors relating to the Company's operations and business 
environment which could change at any time and which may cause the actual 
results of the Company to be materially different from any future results 
expressed or implied by such forward-looking statements. There are inherent 
difficulties in predicting important factors. Potential risks and 
uncertainties include, but are not limited to, changes in customer demand and 
requirements, delays in introducing new products, foreign exchange rates, the 
level of government funding, especially municipalities funding for 
water-related products, changes in federal income tax laws and regulations, 
competition, unanticipated expenses and delays in the integration of any 
newly-acquired business, unanticipated expenses relating to plant 
construction and expansion, the timing and scope of technological advances, 
the ability to attract and retain skilled technical, marketing and management 
personnel, ability to successfully implement its strategies and the soundness 
of those strategies, conditions in the U.S. economy in general and world wide 
economic and business conditions.  The mix of products sold in a quarter is a 
result of a combination of factors, including, but not limited to, changes in 
customer demands and/or requirements, new product announcements, price 
changes, changes in delivery dates, and price competition from other 
suppliers. The Company undertakes no obligation to publicly update or revise 
any forward-looking statements whether as a result of new information, future 
events or otherwise.

                                       2

<PAGE>

                                       PART I

ITEM 1.  BUSINESS

               The Registrant was incorporated in Iowa in 1951 and 
reincorporated in Delaware on April 3, 1968. 

               Additional information required by this item appears under the 
heading "Description of Business" on pages 14 and 15 of the 1998 Annual 
Report and as Note 9 of the Notes to Consolidated Financial Statements, 
"Segment Information," on pages 27 and 28 of the 1998 Annual Report.  

               The Company operates primarily in an industry that encompasses 
laboratory instruments, process analyzers and test kits which analyze the 
chemical content and other properties of water and other aqueous solutions. 
This industry encompasses the chemicals manufactured and sold by the Company, 
most of which are used with the instruments and test kits manufactured by the 
Company. 

               On April 30, 1998, in exchange for approximately $16 million 
in cash and the Company's Common Stocks, the Company acquired Environmental 
Test Systems, Inc., which is engaged in the business of developing and 
manufacturing chemical test strips for measuring water quality for consumer 
and industrial applications.

               Sales for the Company's European subsidiary are made to 
European dealers and to customers in the Middle East and Mediterranean Africa 
in Belgium francs and U.S. dollars, respectively.  Payments from the European 
subsidiary to the U.S. parent are made in U.S. dollars and are subject to the 
exchange rate in effect at the time of payment.  Export transactions made to 
all other parts of the world by the international staff based in Loveland, 
Colorado, are conducted primarily in U.S. dollars. 
 
               The amount of sales made into the international marketplace is 
influenced to some degree by the strength of the U.S. dollar against other 
currencies. Other conditions which to some extent affect the sales of the 
Company's products in international markets include restrictive tariff and 
trade policies imposed by foreign countries, and domestic and foreign tax and 
economic policies.  

ITEM 2.  PROPERTIES

               The principal physical properties of the Registrant are as 
follows: 
 
               The Registrant owns a 150,000 square foot steel frame, 
concrete building situated on 50 acres adjacent to the Loveland, Colorado 
airport at 5600 Lindbergh Drive in Loveland, Colorado.

                                      3

<PAGE>

This building contains the Registrant's executive and administrative offices 
and its research, development, engineering and instrument manufacturing 
operations.  A 66,000 square foot building is under construction at the 
Loveland site and is scheduled for completion in September 1998.  This 
building will house part of the Company's instrument manufacturing operations.

               The Registrant also owns a 169,000 square foot building 
complex situated on 45 acres at 100 Dayton Avenue in Ames, Iowa.  These 
facilities contain chemical manufacturing operations, a chemical research 
laboratory, the home office service function and the shipping department and 
warehouse for all of the products manufactured and sold by the Registrant. 

               The Registrant also owns two buildings totaling 45,000 square 
feet located in Loveland, Colorado.  These buildings contain the Registrant's 
plastic component manufacturing operation, part of the Registrant's component 
assembly operation and an employee training center. 

               The Registrant's wholly-owned subsidiary, Hach Europe, S.A., 
owns a distribution and manufacturing plant containing approximately 44,000 
square feet in Namur, Belgium. 

               The Registrant's wholly-owned subsidiary, Environmental Test 
Systems, Inc. ("ETS") owns a facility in Elkhart, Indiana.  The Elkhart 
Facility is a two-story Varco-Pruden pre-engineered metal building that 
currently comprises 40,000 square feet, with 35,000 square feet of first 
floor manufacturing, office and warehouse space and 5,000 square feet of 
second floor office space. The land at the Elkhart Facility will support 
expansion of an additional 20,000 square feet.

               All of the Registrant's principal physical properties are 
modern and were designed and constructed to the Registrant's specifications 
specifically for use in its business. 

ITEM 3.  LEGAL PROCEEDINGS

               None  

ITEM 4.  SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

               No matters were submitted during the fourth quarter of the 
fiscal year covered by this report to a vote of security holders, through the 
solicitation of proxies or otherwise.

                          EXECUTIVE OFFICERS OF REGISTRANT

<TABLE>
<CAPTION>
Name                     Age       Title
<S>                      <C>       <C>
Kathryn Hach-Darrow      75        Chairman of the Board, Chief Executive
                                    Officer, Chairman of the Executive Committee
                                    and Director

Bruce J. Hach            52        President and Chief Operating Officer and
                                    Director

                                      4

<PAGE>

Robert O. Case           76        Secretary and General Counsel

Gary R. Dreher           45        Vice President and Chief Financial Officer
                                    and Director

Loel J. Sirovy           59        Senior Vice President, Operations

Jerry M. Churchill       58        Vice President, Domestic Sales

Larry D. Thompson        54        Vice President, Ames Chemical Operations

Kenneth Ogan             53        Vice President, Research and Development and
                                    Chief Technical Officer

Brian K. Bowden          33        Vice President, Information Systems
                                    Technology

Mark J. Stephenson       39        Vice President, Marketing and Customer
                                    Support Services - President, ETS
</TABLE>

               Kathryn Hach-Darrow has been active in the business of the 
Registrant since its inception.  She has served on the Board of Directors and 
was responsible, prior to May 6, 1977, as Executive Vice President for 
certain of the Registrant's administrative and marketing matters.  On May 5, 
1977, the Board of Directors elected Mrs. Hach-Darrow President and Chief 
Operating Officer.  On April 28, 1983, she was elected Vice Chairman of the 
Board of Directors and on February 28, 1986, she was elected Chairman of the 
Board, Chief Executive Officer and Chairman of the Executive Committee and 
Director, and has served in these capacities since that date. 

               Bruce J. Hach, son of Kathryn Hach-Darrow, joined the 
Registrant November 1, 1970 and served the Company in various capacities.  
From August 27, 1985 to February 28, 1986, he was an Assistant Vice President 
in charge of Human Relations.  He was elected Senior Vice President on 
February 28, 1986.  On April 30, 1987, he was elected a Director of the 
Registrant, and he was elected Executive Vice President of the Registrant on 
August 27, 1987.  In August 1988, he was elected President and Chief 
Operating Officer of the Registrant and has served in these capacities since 
that date.

               Robert O. Case has been Secretary of the Registrant since May 
29, 1968.  He was named General Counsel to the Registrant on August 29, 1989. 
From September 1989 to February 1991, he was a shareholder of the Chicago, 
Illinois law firm of Schuyler, Roche & Zwirner and a member of its management 
committee.  From February 1, 1991 to April 30, 1993, he was of counsel to 
Schuyler, Roche & Zwirner. Since May 1, 1993, Mr. Case has been of counsel to 
McBride Baker & Coles, a Chicago, Illinois law firm.  Mr. Case was a director 
of the Registrant from May 29, 1968, until his retirement as a Director of 
the Registrant effective at the August 30, 1994 Annual Meeting of 
Shareholders.

                                      5

<PAGE>

               Gary R. Dreher joined the Registrant on January 17, 1977.  He 
has held a variety of positions since then.  In September 1985, he was named 
Controller for the Company.  In August 1990, he was elected Vice President 
and Treasurer of the Registrant.  He was named Vice President and Chief 
Financial Officer on November 22, 1994 and has served in that capacity since 
that date.  He was elected a Director of the Company at the Company's Annual 
Meeting of Shareholders on August 30, 1994.

               Loel J. Sirovy joined the Registrant on October 19, 1972.  He 
has held a number of management positions in Production and Human Relations.  
On September 1, 1985, he was elected Vice President of Instrument Operations. 
On April 28, 1989, he was elected Senior Vice President of Manufacturing.  On 
August 25, 1992, he was elected Senior Vice President of Operations of the 
Registrant and has served in that capacity since that date.

               Jerry M. Churchill joined the Registrant on December 1, 1977, 
as Marketing Manager of Carle Instruments, Inc., which was a wholly-owned 
subsidiary of the Registrant engaged in the manufacturing and sale of gas 
chromatographs.  On April 2, 1981, he was elected Vice President of Carle 
Instruments, Inc.  After Carle Instruments, Inc. was merged into Hach 
Company, Mr. Churchill was made Assistant Vice President of Chromatography 
Operations on September 18, 1983.  On February 28, 1986, he was elected Vice 
President of Domestic Sales and Marketing.  On February 27, 1990, he was 
elected Senior Vice President of Marketing and Sales.  On August 25, 1992, he 
was elected Senior Vice President of Domestic Sales of the Registrant.  On 
August 24, 1993, he was named Vice President of Domestic Sales of the 
Registrant and has served in that capacity since that date.  Mr. Churchill 
was a Director of the Registrant from August 28, 1990, until his retirement 
as a Director of the Registrant effective at the August 29, 1995 Annual 
Meeting of Shareholders.

               Larry D. Thompson joined the Registrant on April 6, 1964.  He 
has held a variety of positions in Chemical Operations.  In April 1991, he 
was named Plant Manager of the Ames, Iowa facility.  On August 25, 1992, he 
was elected Vice President of Ames Chemical Operations of the Registrant and 
has served in that capacity since that date. 

               Kenneth Ogan joined the Registrant in February 1996 as Vice 
President of Research and Development and Chief Technical Officer and has 
served in that capacity since that date.  He most recently served as 
Principal Scientist, Sales and Marketing Division and, prior to that, as 
Senior Manager, Advanced Technology Group for Hitachi Instruments, Inc., 
where he was employed from 1989 through January 1996.  Prior to joining 
Hitachi Instruments, Inc., he was a Group Manager in Instrumentation and 
Research and Development for Perkin-Elmer, Inc.

               Brian K. Bowden joined the Registrant on January 4, 1988.  He 
has held a number of management positions in Research and Development, 
Production, Marketing and Information Services.  On January 7, 1997, he was 
elected Vice President of Information Systems Technology of the Registrant 
and has served in that capacity since that date.

               Mark J. Stephenson joined the Registrant on May 1, 1998, as 
Vice President of Marketing Services and President of the Company's 
subsidiary, ETS.  He most recently served as President 

                                      6

<PAGE>

of ETS prior to its acquisition by the Company on April 30, 1998, and prior 
to that, as Senior Vice President and Vice President of Marketing and Sales 
of ETS, where he was employed since 1988.

               The officers of the Company serve at the pleasure of the Board 
of Directors.

                                      PART II


ITEM 5.  MARKET FOR REGISTRANT'S COMMON EQUITY AND RELATED STOCKHOLDER MATTERS

               The information required by this item appears under the 
heading "Common Stock Price Range and Dividends" on page 15 of the 1998 
Annual Report and is incorporated herein by reference. 

ITEM 6.  SELECTED FINANCIAL DATA

               The information required by this item appears under the 
heading "Comparative Financial Data - 10-Year Summary" on pages 16 and 17 of 
the 1998 Annual Report.

ITEM 7.  MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND 
RESULTS OF OPERATION

               The information required by this item appears in the 
Chairman's and President's letter "To Our Fellow Shareholders" on pages 2, 3 
and 4 of the 1998 Annual Report and under the heading "Management's 
Discussion and Analysis of Financial Condition and Results of Operations" on 
pages 13 and 14 of the 1998 Annual Report, all of which is incorporated 
herein by reference.  

ITEM 8.  FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA

               The information required by this item appears in the 
Consolidated Financial Statements and the Notes thereto on pages 18 through 
28 of the 1998 Annual Report and is incorporated herein by reference.

ITEM 9.  CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING AND 
FINANCIAL DISCLOSURE

Not applicable.

ITEM 10.  DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT

               The information required by this item appears under the 
heading "Election of Directors" on pages 5 and 6 in the 1998 Proxy 
Statement and under the caption "Executive Officers of 

                                      7

<PAGE>

the Registrant" at pages 4 through 7 at the end of Part I of this Report and 
is incorporated by reference.

ITEM 11.  EXECUTIVE COMPENSATION

               The information required by this item appears under the 
heading "Executive Compensation" on pages 8 through 17 in the 1998 Proxy 
Statement, and is incorporated herein by reference.

ITEM 12.  SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

               The information required by this item appears under the 
heading "Beneficial Ownership of Company Securities By Directors, Officers 
and Principal Shareholders" on pages 3 through 5 in the 1998 Proxy Statement, 
and is incorporated herein by reference.

ITEM 13.  CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

               The information required by this item appears under the 
headings "Certain Transactions and Business Relationships" on page 7 of the 
1998 Proxy Statement and "Compensation Committee Interlocks and Insider 
Participation" on page 17 of the 1998 Proxy Statement, and each is 
incorporated herein by reference.

ITEM 14.  EXHIBITS, FINANCIAL STATEMENT SCHEDULES, AND REPORTS ON FORM 8-K

(a)  The following documents are filed as part of this Report on Form 10-K:

1.  FINANCIAL STATEMENTS:  The information required by this item appears on 
the pages listed below in the 1998 Annual Report and is incorporated by 
reference in response to Item 14(a) 1.

<TABLE>
<CAPTION>

                                                                              Page No. in 
                                                                          1998 ANNUAL REPORT
<S>                                                                       <C>
Report of Independent Accountants                                                  18

         Financial Statements:

              Consolidated statements of income for the years
                ended April 30, 1998, 1997 and 1996                                19

              Consolidated balance sheets, April 30, 1998 and 1997                 20

              Consolidated statements of stockholders' equity for the
                years ended April 30, 1998, 1997 and 1996                          21

                                      8

<PAGE>

              Consolidated statements of cash flows for the years
                ended April 30, 1998, 1997 and 1996                                22

              Notes to the consolidated financial statements                       23
</TABLE>

2.  FINANCIAL STATEMENT SCHEDULE:  The following schedule should be read in 
conjunction with the consolidated financial statements incorporated by 
reference in Item 8 of this Form 10-K.  Schedules other than that listed 
have been omitted because they are not applicable or not required.  

<TABLE>
<CAPTION>

                                                    Page No. in
           Schedule                                 this Report
           --------                                 -----------
<S>                                                 <C>
 Report of Independent Accountants on the
      Financial Statement Schedule                     14
 Valuation and Qualifying Accountants                  15
      (Schedule II)

</TABLE>

3.  EXHIBITS REQUIRED BY ITEM 601 OF REGULATION S-K:  The following exhibits are
included in this Annual Report on Form 10-K.  The items identified below as
Exhibits (10)c - (10)l. are management contracts or compensatory plans required
to be filed as an Exhibit to this Annual Report on Form 10-K pursuant to Item
14(c) on Form 10-K.

<TABLE>
<CAPTION>

NO. ASSIGNED IN
EXHIBIT TABLE ON                                                                     PAGE NO. IN
ITEM 601 OF REG. S-K               EXHIBIT                                           THIS REPORT
<S>                      <C>                                                         <C>
(3)                      a.   Restated Certificate of Incorporation of the 
                              Registrant -- hereby incorporated by reference
                              to Exhibit 99.2 to the Registrant's Quarterly
                              Report on Form 10-Q for the quarter ended
                              October 26, 1996, Commission File No. 0-3947; 
                              Certificate of Amendment to Article Fourth of 
                              the Restated Certificate of Incorporation of 
                              the Registrant as filed with the Delaware 
                              Secretary of State on September 10, 1997 -- 
                              hereby incorporated by reference to Exhibit 1.2 
                              to the Company's Registration Statement on Form 
                              8-A, Commission File No. 0-3947, as filed with 
                              the Commission on September 10, 1997.

(3)                      b.   By-laws of the Registrant, as amended and 
                              restated through October 26, 1996 -- hereby 
                              incorporated by reference to Exhibit 99.3 to the 
                              Registrant's Quarterly Report on Form 10-Q for 
                              the quarter ended October 26, 1996, Commission 
                              File No. 0-3947.

(10)                     c.   Hach Company 1993 Stock Option Plan as Amended
                              and Restated as of November 25, 1997.

(10)                     d.   Form of Stock Option Agreement under 1993 Stock
                              Option Plan -- hereby incorporated by reference to 
                              Exhibit (10)d. to the Registrant's Annual Report

                                      9

<PAGE>

                              on form 10-K for the year ended April 30, 1994,
                              Commission file No. 0-3947.

(10)                     e.   Hach Company Restated 1983 Stock Option Plan --
                              hereby incorporated by reference to Exhibit (10) d.
                              to the Registrant's Annual Report on Form 10-K for
                              the year ended April 30, 1993, Commission File No. 0-3947.

(10)                     f.   Form of Stock Option Agreements for 1983 Stock
                              Option Plan -- hereby incorporated by reference to 
                              Exhibit (10)e. of the Registrant's Annual Report on
                              Form 10-K for the fiscal year ended April 30, 1991,
                              Commission File No. 0-3947.

(10)                     g.   Hach Company Restated Director's Bonus Compensation
                              Plan -- hereby incorporated by reference to Exhibit (10)f.
                              of the Registrant's Annual Report on Form 10-K for the 
                              fiscal year ended April 30, 1991, Commission File No.
                              0-3947;  Fifth Amendment to Directors Bonus
                              Compensation Plan -- hereby incorporated by reference to
                              Exhibit (10)g. to the Registrant's Annual Report on
                              Form 10-K for the year ended April 30, 1996,
                              Commission File No. 0-3947.

(10)                     h.   Executive Employment Agreements between the Company
                              and each of Bruce J. Hach, Loel J. Sirovy,
                              Jerry M. Churchill, Gary R. Dreher, and Larry D. Thompson -- 
                              hereby incorporated by reference to Exhibit 10(h). to the 
                              Registrant's Annual Report on Form 10-K for the year ended 
                              April 30, 1994, Commission File No. 0-3947;  
                              Executive Employment Agreement between the Company
                              and Kenneth Ogan -- hereby incorporated by reference to 
                              Exhibit (10)h. to the Registrant's Annual Report on Form 10-K
                              for the year ended April 30, 1996, Commission File No. 0-3947; 
                              Employment Agreement between the Company and 
                              Mark Stephenson dated April 30, 1998.

(10)                     i.   Hach Company 1995 Employee Stock Purchase Plan as Amended 
                              and Restated as of January 1, 1998.

(10)                     j.   Hach Company Deferred Compensation Plan (as amended
                              through March 1, 1995) -- hereby incorporated by reference
                              to Exhibit (10)j. of the Registrant's Annual Report on Form
                              10-K for the fiscal year ended April 30, 1995, Commission
                              File No. 0-3947.

                                      10

<PAGE>

(10)                     k.   Trust Under Hach Company Deferred Compensation Plan 
                              dated as of April 10, 1995 between the Company and the
                              Dauphin Deposit Bank and Trust Company, as trustee
                              hereby incorporated by reference to Exhibit (10)k. of the
                              Registrant's Annual Report on Form 10-K for the fiscal
                              year ended April 30, 1995, Commission File No. 0-3947.

(10)                     l.   Hach Company 1995 Non-Employee Director Stock Plan 
                              Amended and Restated as of November 25, 1997.

(10)                     m.   Revolving Credit Agreement dated as of July 7, 1997 
                              among the Registrant, Hach Europe S.A. and Colorado 
                              National Bank--hereby incorporated by reference to Exhibit 
                              (10)m. to the Registrant's Annual Report on Form 10-K for 
                              the year ended April 30, 1997, Commission File No. 0-3947.

(13)                     n.   Pages 2, 3, 4 and 13 through 28 of the Registrant's Annual
                              Report to Stockholders for the year ended April 30, 1998.

(21)                     o.   Subsidiaries of the Registrant.

(23)                     p.   Consent of PricewaterhouseCoopers LLP

(27)                     q.   Financial Data Schedules (electronic filing only)


(b)                      No reports on Form 8-K were filed during the quarter ended April 30, 1998.

(c) and (d)              The exhibits and financial statement schedules required to be filed by this 
                         item are attached to or incorporated by reference in this report.

</TABLE>

                                      11

<PAGE>

                                  SIGNATURES

               Pursuant to the requirements of Section 13 or 15(d) 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.

                                HACH COMPANY

July 29, 1998          By: /s/  Kathryn Hach-Darrow
-------------              ------------------------------------------------
Date                       Kathryn Hach-Darrow, Chairman of the Board, 
                           Chief Executive Officer

               Pursuant to the requirements of the Securities Exchange Act of 
1934, this report has been signed below by the following persons on behalf of 
the registrant and in the capacities and on the dates indicated.

July 29, 1998          By:  /s/  Kathryn Hach-Darrow
-------------              ------------------------------------------------
Date                       Kathryn Hach-Darrow, Chairman of the Board, 
                           Chief Executive Officer and Director



July 29, 1998          By:  /s/  Gary R. Dreher
-------------              ------------------------------------------------
Date                       Gary R. Dreher, Vice President, Chief Financial 
                           Officer, Principal Accounting Officer and Director

July 29, 1998          By:  /s/  Bruce J. Hach                           
-------------              ------------------------------------------------
Date                       Bruce J. Hach, Director

July 29, 1998          By:  /s/  Fred W. Wenninger
-------------              ------------------------------------------------
Date                       Fred W. Wenninger, Director

July 29, 1998          By:  /s/  Joseph V. Schwan 
-------------              ------------------------------------------------
Date                       Joseph V. Schwan, Director

                                      12

<PAGE>

July 29, 1998          By:  /s/  John N. McConnell
-------------              ------------------------------------------------
Date                       John N. McConnell, Director

July 29, 1998          By:  /s/  Linda O. Doty                           
-------------              ------------------------------------------------
Date                       Linda O. Doty, Director

                                      13

<PAGE>

Report of Independent Accountants on the Financial Statement Schedule



To the Board of Directors of Hach Company


Our audits of the consolidated financial statements referred to in our report 
dated June 4, 1998 appearing in the 1998 Annual Report to Shareholders of 
Hach Company and Subsidiaries (which report and consolidated financial 
statements are incorporated by reference in this Annual Report on Form 10-K) 
also included an audit of the Financial Statement Schedule included in Item 
14(a)(2) of this Form 10-K.  In our opinion, the Financial Statement Schedule 
presents fairly, in all material respects, the information set forth therein 
when read in conjunction with the related consolidated financial statements.

PricewaterhouseCoopers LLP

Denver, Colorado
June 4, 1998

                                      14

<PAGE>

               SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS
                   Year Ended April 30, 1998, 1997 and 1996
                            (In thousands)
                                             

<TABLE>
<CAPTION>
                                                   Balance at            Charged to                                 Balance
                                                   beginning             costs and            Deductions            at end
                                                   of period              expenses            /(Writeoff)          of period
                                                   --------------------------------------------------------------------------
<S>                                                <C>                   <C>                  <C>                   <C>
Allowance for Doubtful Accounts:
   Year ended April 30, 1998                        $    249             $       72           $      (16)           $     305
   Year ended April 30, 1997                             248                     69                  (68)                 249
   Year ended April 30, 1996                             247                     87                  (86)                 248
Inventory Reserve:
   Year ended April 30, 1998                        $    555             $    1,317           $     (869)           $   1,003
   Year ended April 30, 1997                             188                  1,369               (1,002)                 555
   Year ended April 30, 1996                             505                    245                 (562)                 188

</TABLE>

<PAGE>

                                 INDEX TO EXHIBITS
<TABLE>
<CAPTION>


NO. ASSIGNED IN
EXHIBIT TABLE ON                                                                         PAGE NO. IN
ITEM 601 OF REG. S-K                    EXHIBIT                                          THIS REPORT
<S>                      <C>                                                             
(3)                      a.   Restated Certificate of Incorporation of the
                              Registrant -- hereby incorporated by reference
                              to Exhibit 99.2 to the Registrant's Quarterly
                              Report on Form 10-Q for the quarter ended
                              October 26, 1996, Commission File No. 0-3947; 
                              Certificate of Amendment to Article Fourth of 
                              the Restated Certificate of Incorporation of 
                              the Registrant as filed with the Delaware 
                              Secretary of State on September 10, 1997 -- 
                              hereby incorporated by reference to Exhibit 1.2 
                              to the Company's Registration Statement on Form 
                              8-A, Commission File No. 0-3947, as filed with 
                              the Commission on September 10, 1997.

(3)                      b.   By-laws of the Registrant, as amended through
                              October 26, 1996 -- hereby incorporated by reference
                              to Exhibit 99.3 to the Registrant's Quarterly Report
                              on Form 10-Q for the quarter ended October 26, 1996,
                              Commission File No. 0-3947.

(10)                     c.   Hach Company 1993 Stock Option Plan as Amended
                              and Restated as of November 25, 1997.
                    
(10)                     d.   Form of Stock Option Agreement under 1993 Stock
                              Option Plan -- hereby incorporated by reference to 
                              Exhibit (10)d. to the Registrant's Annual Report
                              on form 10-K for the year ended April 30, 1994,
                              Commission file No. 0-3947.

(10)                     e.   Hach Company Restated 1983 Stock Option Plan --
                              hereby incorporated by reference to Exhibit (10) d.
                              to the Registrant's Annual Report on Form 10-K for
                              the year ended April 30, 1993, Commission File No. 0-3947.

(10)                     f.   Form of Stock Option Agreements for 1983 Stock
                              Option Plan -- hereby incorporated by reference to 
                              Exhibit (10)e. of the Registrant's Annual Report on
                              Form 10-K for the fiscal year ended April 30, 1991,
                              Commission File No. 0-3947.

(10)                     g.   Hach Company Restated Director's Bonus Compensation
                              Plan -- hereby incorporated by reference to Exhibit (10)f.
                              of the Registrant's Annual Report on Form 10-K for the 
                              fiscal year ended April 30, 1991, Commission File No.
                              0-3947;  Fifth Amendment to Directors Bonus
                              Compensation Plan -- hereby incorporated by reference to
                              Exhibit (10)g. to the Registrant's Annual Report on

<PAGE>

                              Form 10-K for the year ended April 30, 1996,
                              Commission File No. 0-3947.

(10)                     h.   Executive Employment Agreements between the Company
                              and each of Bruce J. Hach, Loel J. Sirovy,
                              Jerry M. Churchill, Gary R. Dreher, and Larry D. Thompson -- 
                              hereby incorporated by reference to Exhibit 10(h). to the 
                              Registrant's Annual Report on Form 10-K for the year ended 
                              April 30, 1994, Commission File No. 0-3947;  
                              Executive Employment Agreement between the Company
                              and Kenneth Ogan -- hereby incorporated by reference to 
                              Exhibit (10)h. to the Registrant's Annual Report on Form 10-K
                              for the year ended April 30, 1996, Commission File No. 0-3947; 
                              Employment Agreement between the Company and 
                              Mark Stephenson dated April 30, 1998.

(10)                     i.   Hach Company 1995 Employee Stock Purchase Plan 
                              as Amended and Restated as of January 1, 1998.

(10)                     j.   Hach Company Deferred Compensation Plan (as amended
                              through March 1, 1995) -- hereby incorporated by reference
                              to Exhibit (10)j. of the Registrant's Annual Report on Form
                              10-K for the fiscal year ended April 30, 1995, Commission
                              File No. 0-3947.

(10)                     k.   Trust Under Hach Company Deferred Compensation Plan 
                              dated as of April 10, 1995 between the Company and the
                              Dauphin Deposit Bank and Trust Company, as trustee
                              hereby incorporated by reference to Exhibit (10)k. of the
                              Registrant's Annual Report on Form 10-K for the fiscal
                              year ended April 30, 1995, Commission File No. 0-3947.

(10)                     l.   Hach Company 1995 Non-Employee Director Stock Plan 
                              Amended and Restated as  of November 25, 1997.

(10)                     m.   Revolving Credit Agreement dated as of July 7, 1997 
                              among the Registrant, Hach Europe S.A. and 
                              Colorado National Bank-- hereby incorporated by reference to 
                              Exhibit (10)m. to the Registrant's Annual Report on Form 10-K for 
                              the year ended April 30, 1997, Commission File No. 0-3947.

(13)                     n.   Pages 2, 3, 4 and 13 through 28 of the Registrant's Annual
                              Report to Stockholders for the year ended April 30, 1998.

(21)                     o.   Subsidiaries of the Registrant.

<PAGE>

(23)                     p.   Consent of PricewaterhouseCoopers LLP

(27)                     q.   Financial Data Schedules (electronic filing only)

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