SCHEDULE 14A
                            SCHEDULE 14A INFORMATION
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                           Meridian Diagnostics, Inc.
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                (Name of Registrant as Specified In Its Charter)

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                           MERIDIAN DIAGNOSTICS, INC.
                             3471 River Hills Drive
                             Cincinnati, Ohio 45244


                            Notice of Annual Meeting
                               and Proxy Statement


Dear Shareholder:

Our annual  shareholders'  meeting will be held at 3:00 p.m. on January 20, 2000
at The Phoenix, 812 Race Street,  Cincinnati,  Ohio. We hope you will attend. At
the meeting,  you will hear a report on our operations and have a chance to meet
your directors and executives.

This booklet  includes the formal notice of the meeting and the proxy statement.
The proxy  statement  tells you more  about the agenda  and  procedures  for the
meeting. It also describes how the Board operates and gives personal information
about our director candidates.

We want your shares to be  represented  at the meeting.  I urge you to complete,
sign, date, and return your proxy card promptly in the enclosed envelope.

Sincerely yours,


/s/ William J. Motto

William J. Motto
Chairman of the Board

December 16, 1999






                            NOTICE OF ANNUAL MEETING
                                       OF
                   SHAREHOLDERS OF MERIDIAN DIAGNOSTICS, INC.




Time:

          3:00 p.m., Eastern Time

Date:

          January 20, 2000

Place:

          The Phoenix
          812 Race Street
          Cincinnati, Ohio

Purpose:

     -    Elect directors

     -    Ratify appointment of Arthur Andersen LLP as the Company's independent
          public accountants for fiscal year 2000 .

     -    Conduct other business if properly raised


     Only  shareholders  of record on December 3, 1999 may vote at the  meeting.
The approximate mailing date of this Proxy Statement and accompanying Proxy Card
is December 17, 1999.


Your vote is important.  Please complete, sign, date, and return your proxy card
promptly in the enclosed envelope.



/s/ Gerard Blain

Gerard Blain
Secretary

December 16, 1999




                               TABLE OF CONTENTS

                                                                            Page


GENERAL INFORMATION...........................................................1
ELECTION OF DIRECTORS.........................................................1
RATIFICATION OF APPOINTMENT OF ACCOUNTANTS....................................3
DIRECTOR COMPENSATION.........................................................3
BOARD COMMITTEES..............................................................3
COMPENSATION COMMITTEE REPORT ON EXECUTIVE COMPENSATION.......................3
PRINCIPAL SHAREHOLDER.........................................................4
DIRECTORS AND EXECUTIVE OFFICERS..............................................5
SECTION 16 BENEFICIAL OWNERSHIP REPORTING COMPLIANCE..........................6
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION...................6
SUMMARY COMPENSATION TABLE....................................................6
OPTION GRANTS IN LAST FISCAL YEAR.............................................7
FISCAL 1999 OPTION EXERCISES AND FISCAL YEAR-END OPTION VALUES................7
PERFORMANCE GRAPH.............................................................8
SHAREHOLDER PROPOSALS FOR NEXT YEAR...........................................9
QUESTIONS?....................................................................9





                              GENERAL INFORMATION

Who may vote

Shareholders of Meridian, as recorded in our stock register on December 3, 1999,
may vote at the  meeting.  As of that date,  Meridian had  14,585,081  shares of
Common Stock outstanding.

How to vote

You may vote in person at the  meeting  or by proxy.  We  recommend  you vote by
proxy even if you plan to attend the meeting. You can always change your vote at
the meeting.

How proxies work

Meridian's  Board of  Directors  is asking for your proxy.  Giving us your proxy
means you  authorize  us to vote your  shares at the  meeting  in the manner you
direct. You may vote for all, some, or none of our director candidates.
You may also vote for or against the other proposals or abstain from voting.

If you sign and return the  enclosed  proxy card but do not specify how to vote,
we will vote your shares in favor of our director candidates and in favor of the
ratification  of  Arthur  Andersen  LLP  as  the  Company's  independent  public
accountants for fiscal year 2000.

You may  receive  more than one proxy or voting card  depending  on how you hold
your shares.  Shares registered in your name are covered by one card. And if you
hold shares through  someone else,  such as a stockbroker,  you may get material
from them asking how you want to vote.

Revoking a proxy

You may revoke your proxy  before it is voted by  submitting  a new proxy with a
later  date,  by voting in person at the  meeting,  or by  notifying  Meridian's
Secretary in writing at the address under "Questions?" on page 9.

Quorum

In order to carry on the  business of the meeting,  we must have a quorum.  This
means at least a majority  of the  outstanding  shares  eligible to vote must be
represented at the meeting, either by proxy or in person.

Votes needed

The five  director  candidates  receiving the most votes will be elected to fill
the seats on the Board.  Approval of the other  proposal  requires the favorable
vote of a  majority  of the votes  cast.  Only  votes for or  against a proposal
count.  Abstentions  and broker  non-votes count for quorum purposes but not for
voting  purposes.  Broker non-votes occur when a broker returns a proxy card but
does not have authority to vote on a particular proposal.

Other Matters

Any other matters considered at the meeting, including adjournment, will require
the affirmative vote of a majority of shares voting.

Voting by Proxy

All proxies  properly signed will,  unless a different  choice is indicated,  be
voted "FOR" the election of all nominees for Directors  proposed by the Board of
Directors  and  "FOR"  ratification  of  the  selection  of  independent  public
accountants.

If any other matters come before the meeting or any adjournment, each proxy will
be voted in the discretion of the individuals named as proxies on the card.




                              ELECTION OF DIRECTORS
                           (Item 1 on the Proxy Card)

The Board has nominated the director candidates named below.

The Board of Directors  oversees the  management  of the Company on your behalf.
The Board reviews  Meridian's  long-term  strategic  plans and exercises  direct
decision-making  authority in key areas,  such as choosing  the Chief  Executive
Officer, setting the scope of his authority to manage the company's business day
to day, and evaluating management's performance.

The Board is nominating for reelection all of the following  current  directors:
James A. Buzard, John A. Kraeutler, Gary P. Kreider, William J. Motto and Robert
J. Ready.

Proxies solicited by the Board will be voted for the election of these nominees.
All directors elected at the Annual Meeting will be elected to hold office until
the next annual meeting. In voting to elect directors, shareholders are entitled
to cumulate their votes and to give one candidate a number of votes equal to the
number of directors to be elected multiplied by the number of shares held by the
shareholder,  or to distribute  their votes on the same principle  among as many
candidates as the shareholder  sees fit. In order to invoke  cumulative  voting,
notice of  cumulative  voting must be given in writing by a  shareholder  to the
President,  a Vice President or the Secretary of Meridian not less than 48 hours
prior  to the  Annual  Meeting.  The  proxies  solicited  include  discretionary
authority to cumulate their votes.

Three  of our  five  nominees  are not  Meridian  employees.  Only  non-employee
directors serve on Meridian's  Audit and Compensation  committees.  All Meridian
directors are elected for one-year  terms.  Personal  information on each of our
nominees is given below.

Board meetings last year:  5
Actions in writing last year:  0

If a director nominee becomes  unavailable before the election,  your proxy card
authorizes us to vote for a replacement nominee if the Board names one.

Nominees  receiving  the highest  number of votes cast for the  positions  to be
filled will be elected.

The Board recommends you vote FOR each of the following candidates:

James A. Buzard, Ph.D.  James  A.  Buzard,  Ph.D.  serves  as  Chairman  of  the
Age 72                  Compensation Committee.  From  March 1981 until December
Director since 1990     1989,  he  was  Executive  Vice President of Merrell Dow
                        Pharmaceuticals  Inc.  From  December  1989  until   his
                        retirement  in  February  1990, he was Vice President of
                        Marion  Merrell  Dow,  Inc.  He  has  been  a   business
                        consultant since February 1990.
- --------------------------------------------------------------------------------
John A. Kraeutler       John A. Kraeutler  has more  than 20 years of experience
Age 51                  in  the  medical  diagnostics industry  and  joined  the
Director since 1997     Company  as Executive Vice President and Chief Operating
                        Officer in January  1992.  In  July 1992,  Mr. Kraeutler
                        was  named  President  of  the  Company.  Before joining
                        Meridian,  Mr. Kraeutler  served  as  Vice    President,
                        General  Manager for  a division of Carter-Wallace, Inc.
                        Prior  to  that,  he  held  key  marketing and technical
                        positions  with  Becton,  Dickinson  and   Company   and
                        Organon, Inc.
- --------------------------------------------------------------------------------
Gary P. Kreider, Esq.   Gary  P.  Kreider  has  been  a  Senior  Partner  of the
Age 61                  Cincinnati  law  firm  of  Keating,  Muething & Klekamp,
Director since 1991     P.L.L., counsel  to the  Company since 1975.  He is also
                        an  Adjunct  Professor  of  Law  in  securities  at  the
                        University of Cincinnati College of Law.
- --------------------------------------------------------------------------------
William J. Motto        William J. Motto has more than 25 years of experience in
Age 58                  the pharmaceutical and diagnostics  products industries,
Director since 1977     is a founder of the Company and has been Chairman of the
                        Board since 1977.  Before forming the Company, Mr. Motto
                        served  in  various capacities for Wampole Laboratories,
                        Inc., Marion Laboratories, Inc.  and Analytab  Products,
                        Inc., a division of American Home Products Corp.
- --------------------------------------------------------------------------------






Robert J. Ready       Robert J. Ready serves as Chairman of the Audit Committee.
Age 59                In  1976,  Mr.  Ready  founded  LSI  Industries,     Inc.,
Director since 1986   Cincinnati,  Ohio,   which   engineers,  manufactures  and
                      markets   commercial/industrial  lighting   and   graphics
                      products,  and has served as its President and Chairman of
                      its Board of Directors since that time.
- --------------------------------------------------------------------------------


                   RATIFICATION OF APPOINTMENT OF ACCOUNTANTS
                           (Item 2 on the Proxy Card)

Although not  required,  the Board is seeking  shareholder  ratification  of its
selection of Arthur Andersen LLP as the Company's independent public accountants
for fiscal  2000.  An  affirmative  vote of a majority  of shares  voting at the
meeting is required for ratification. If ratification is not obtained, the Board
intends to continue  the  employment  of Arthur  Andersen  LLP at least  through
fiscal 2000.  Representatives  of Arthur Andersen LLP are expected to be present
at the  Shareholders'  Meeting and will be given an opportunity  to comment,  if
they so desire,  and to respond to  appropriate  questions  that may be asked by
shareholders.

DIRECTOR COMPENSATION

Non-employee  directors  of Meridian  receive  $12,000 per year for serving as a
director and as members of committees of the Board. They also receive $1,000 for
each  director or  committee  meeting  attended,  except if a committee  meeting
occurs on the same day as a directors'  meeting and then the  committee  meeting
fee is $800.  They receive $500 for each  director or committee  meeting held by
telephone.  Committee  chairmen  receive an additional  $500 for each  committee
meeting held. Each non-employee  director is also granted a non-qualified option
to purchase  2,317 shares of Common Stock at the time of election or re-election
to the Board of Directors,  with the exercise price being the closing sale price
reported immediately prior to the date of grant.  Directors who are employees of
Meridian are not separately compensated for serving as directors.

BOARD COMMITTEES

The Board appoints committees to help carry out its duties. In particular, Board
committees  work on key issues in greater  detail than would be possible at full
Board meetings. Each committee reviews the results of its meetings with the full
Board. The Board of Directors does not have a nominating  committee or executive
committee.

The  Audit  Committee  is  responsible  for  reviewing  the  Company's  internal
accounting  operations.   It  also  recommends  the  employment  of  independent
accountants  and  reviews the  relationship  between the Company and its outside
accountants.

Committee members: Messrs. Buzard, Kreider and
Ready (Chairman).

Meetings last year: 4
Actions in writing last year: 0

The  Compensation  Committee is responsible for  establishing  compensation  for
management and administering the Company's stock option plans.

Committee members: Messrs. Buzard (Chairman),
Kreider and Ready.

Meetings last year: 3
Actions in writing last year: 4

COMPENSATION COMMITTEE REPORT ON EXECUTIVE
COMPENSATION
Report of the Compensation Committee

The  Compensation  Committee  is  charged  with  establishing  compensation  for
executive officers through the establishment of salaries and bonus plans as well
as making bonus awards and awarding stock options.

At a meeting held  September 17, 1998,  the Committee set salaries for executive
officers for fiscal 1999. In establishing these salaries, the Committee reviewed
background  information  showing the fiscal  1998  compensation  for  Meridian's
executives,  along  with  comparisons  of  certain  peer  companies  as  well as
comparisons with the instruments and biomedical equipment and supply group. This
process allowed  increases to be tied more to the executives'  responsibilities,
development and contributions to Meridian's operations.  The salary of the Chief
Executive Officer, Mr. Motto, was determined in the same manner.






At a meeting  held  November  17, 1999,  the  Committee  reviewed the bonus plan
adopted for fiscal 1999 and confirmed the award of bonuses  pursuant to the plan
since the earnings  targets set in the plan were  achieved.  The Committee  also
awarded special bonuses of $25,000 each to Messrs. Blain, Eberly,  Kraeutler and
Motto  reflecting  their  extraordinary  efforts  in  the  acquisition  of  Gull
Laboratories.  The Committee also established a bonus plan for fiscal 2000. This
plan calls for the award of bonuses if designated  net earnings  levels are met.
The amount of each bonus is  determined  by  multiplying  base  compensation  by
percentages keyed to earnings levels,  and then applying a personal  achievement
multiplier to that result.  The methodology of this plan is the same as employed
in the past several years.  At other meetings  during fiscal 1999, the Committee
awarded  options  from the  Company's  previously  approved  Stock  Option  Plan
reflecting its view of the importance of particular  executives to the Company's
future performance.

                                             Compensation Committee of
                                             the Board of Directors



                                             James A. Buzard, Chairman
                                             Gary P. Kreider
                                             Robert J. Ready








                              PRINCIPAL SHAREHOLDER

The  following  person  is the  only  shareholder  known by the  Company  to own
beneficially 5% or more of its outstanding Common Stock as of December 3, 1999:


                               Amount and Nature of            Percent
Name of Beneficial Owner       Beneficial Ownership           of Class
- ------------------------       --------------------           --------
William J. Motto                    4,634,936                    31.7%

The business  address of Mr. Motto is 3471 River Hills Drive,  Cincinnati,  Ohio
45244.

Mr. Motto is a party to an agreement  with Jerry L. Ruyan and Meridian  pursuant
to which he must offer his shares for sale to  Meridian,  and if it  declines to
purchase, to Mr. Ruyan, based on the current market price, if he desires to sell
more than 1% of Meridian's Common Stock in any three-month period.

The shares of Common Stock reported as  beneficially  owned by Mr. Motto include
706,399 shares held by his three children as trustees of various trusts,  51,646
shares held by the William J. Motto  Family  Charitable  Remainder  Unitrust and
13,300 shares subject to options exercisable within 60 days.





DIRECTORS AND EXECUTIVE OFFICERS

This table lists the executive  officers and directors of Meridian and shows how
much common stock each owned on December 3, 1999.



                                                                                   Common Stock
                                                                                Beneficially Owned
                                                                             -------------------------
        Name and Age                        Position                           Amount1      Percentage
        ------------                        --------                         ---------      ----------
                                                                                      
William J. Motto              Chairman of the Board of Directors,            4,634,9362        31.7%
58                            Chief Executive Officer
John A. Kraeutler             President, Chief Operating Officer                155,325           *
51                            and Director
Gerard Blain3                 Executive Vice President, Chief                    48,645           *
59                            Financial Officer and Secretary
Antonio A. Interno4           Senior Vice President                             365,885         2.5%
49
Richard L. Eberly5            Vice President, Sales and Marketing                13,050           *
38
Kenneth J. Kozak6             Vice President, Research and                        1,072           *
45                            Development
James A. Buzard, Ph.D.7       Director                                           21,759           *
72
Gary P. Kreider7              Director                                          37,2618           *
61
Robert J. Ready7              Director                                           24,464           *
59
                                                                              ---------
All Executive Officers and                                                    5,302,397         35.5%
Directors as a Group

<FN>

1.       Includes  options  exercisable  within 60 days from Mr. Motto of 13,300
         shares,  Mr.  Kraeutler of 150,973 shares,  Mr. Blain of 46,210 shares,
         Mr. Interno of 51,866 shares,  Mr. Eberly of 12,750 shares,  Mr. Buzard
         of 20,507 shares,  Mr.  Kreider of 13,904  shares,  Mr. Ready of 23,014
         shares and Mr. Kozak of 1,072 shares.
2.       See  description of Common Stock ownership contained  under  "Principal
         Shareholder."
3.       Gerard Blain joined the Company as Vice  President and Chief  Financial
         Officer on March 1, 1994. He was elected Secretary in April 1996. Prior
         to joining the Company,  Mr. Blain was Vice President and Controller of
         Marion  Merrell Dow,  Inc. Mr. Blain had been with Marion  Merrell Dow,
         Inc. and its  predecessor  companies  since 1966.  Mr. Blain also holds
         Meridian debentures convertible into 621 shares.
4.       Antonio A. Interno was appointed as a Vice President in August 1991 and
         appointed  a Senior  Vice  President  in  September  1997.  He has been
         Managing  Director  of  the  Company's  European  subsidiary,  Meridian
         Diagnostics  Europe since February 1990. Prior to that time, he was the
         marketing  manager for Diagnostics  International  Distribution  SPA, a
         major Italian diagnostics distributor.
5.       Richard L. Eberly was appointed  Vice  President of Sales and Marketing
         on January 10, 1997.  He has over 12 years of experience in the medical
         diagnostic  industry and joined the Company in January  1995.  Prior to
         his  appointment to Vice  President of Sales and Marketing,  Mr. Eberly
         served  as the  Director  of  Sales  for the  Company.  Before  joining
         Meridian  he  held  key  sales  and   marketing   positions  at  Abbott
         Diagnostics.
6.       Kenneth J. Kozak joined the Company in October  1987 and was  appointed
         Vice President,  Research and  Development,  on May 17, 1999.  Prior to
         this appointment,  Mr. Kozak served as Director of Product  Development
         for the Company.  Before joining Meridian,  Mr. Kozak held a variety of
         positions at the University of Cincinnati College of Medicine.
7.       Audit Committee Member and Compensation Committee Member.
8.       Includes 145 shares held  directly by his wife and 9,564 shares held by
         trusts of which Mr. Kreider is trustee and a  beneficiary.  Mr. Kreider
         also holds Meridian debentures convertible into 1,491 shares.

* Less than one percent.

</FN>





SECTION 16 BENEFICIAL OWNERSHIP REPORTING COMPLIANCE

     Section 16 of the  Securities  Exchange Act of 1934  requires the Company's
executive  officers,  directors  and  persons who own more than ten percent of a
registered class of the Company's equity securities to file reports of ownership
and changes in ownership. Based on a review of the copies of such forms received
by it, the  Company  believes  that  during  the last  fiscal  year,  all of its
executive  officers,  directors and ten percent  stockholders  complied with the
Section 16 reporting requirements. COMPENSATION COMMITTEE INTERLOCKS AND INSIDER
PARTICIPATION

     Gary P. Kreider, who is a member of the Compensation Committee, is a senior
partner of Keating,  Muething & Klekamp,  P.L.L.,  Cincinnati,  Ohio, a law firm
that provided legal services to Meridian in fiscal 1999.


                           SUMMARY COMPENSATION TABLE


                                            Annual Compensation
                         -------------------------------------------------------
                                                       Securities
Name and                                              Underlying     All Other
Principal Position      Year     Salary      Bonus     Options     Compensation1
- ---------------------   ----   ---------  ---------   ----------   -------------

William J. Motto        1999   $ 355,000  $ 144,813         -       $ 24,313
Chairman of the Board   1998     338,000          -         -         29,312
of Directors, Chief     1997     325,000          -         -         20,908
Executive Office

John A. Kraeutler       1999   $ 257,000  $ 111,738    50,000       $ 17,010
President, Chief        1998     245,000          -    50,000         15,635
Operating Officer       1997     235,000          -         -         11,463

Gerard Blain            1999   $ 185,000    $87,438    10,000        $14,113
Executive Vice          1998     162,000          -    50,000         23,918
President, Chief        1997     147,000          -         -         13,015
Financial Officer
and Secretary

Antonio A. Interno      1999   $ 210,000    $59,527         -         $    0
Vice President          1998     200,000          -     7,000              0
                        1997     190,700          -         -              0

Richard L. Eberly       1999   $ 116,000    $64,150     7,500       $ 18,362
Vice President, Sales   1998     110,000      9,400    10,500          9,719
                        1997     100,000          -     9,100          4,503


1    Amounts  accrued  under the Company's  Savings and  Investment  Plan.  Also
     includes certain  education  related  expenses,  professional  fees and car
     allowances,  as well as  premiums  paid  under the  Company's  Split-Dollar
     Insurance Program.  The Company maintains a Split-Dollar  Insurance Program
     for selected  individuals.  Under this  Program,  the Company has purchased
     insurance policies on the lives of Mr. Motto, Mr. Kraeutler, Mr. Eberly and
     Mr. Blain.  These individuals are responsible for a portion of the premiums
     and the  Company  pays  the  remainder.  Upon  the  death  of any of  these
     individuals,  the Company will  receive  that portion of the benefits  paid
     that equals the premiums paid by the Company on the respective  policy. The
     beneficiary  named by the decedent  will receive the remainder of the death
     benefits.  The premiums  paid to the insurer  under these  policies for the
     fiscal years ended September 1999, 1998 and 1997 were $10,411, $15,033, and
     $16,166,   respectively,   for  Mr.  Motto;  $7,058,   $5,791  and  $6,822,
     respectively, for Mr. Kraeutler; $755, $596 and $773, respectively, for Mr.
     Eberly; $0, $10,385 and $8,422, respectively, for Mr. Blain.






     Todd Motto,  the adult son of William J. Motto, is the Director of Business
     Development at Meridian  Diagnostics,  Inc. Todd Motto received  $84,835 in
     compensation for fiscal 1999.





                        OPTION GRANTS IN LAST FISCAL YEAR


                                   % of Total
                     Number of       Options                                   Potential Realized Value
                     Securities     Granted to                                      at Assumed Annual
                     Underlying     Employees                                  Rates of Price Appreciation
                       Options      in Fiscal    Exercise Price  Expiration       for Option Term
    Name               Granted         1999      ($/Per Share)      Date         5%            10%
- -----------------    ---------     -----------   --------------  ----------   --------       --------
                                                                           
John A. Kraeutler      50,000         38.2%          $6.750       10/29/08    $549,752       $875,388
Gerard Blain           10,000          7.6%          $6.750       10/29/08    $109,950       $175,078
Richard L. Eberly       7,500          5.7%          $6.440        4/19/09    $ 78,676       $125,278





          FISCAL 1999 OPTION EXERCISESAND FISCAL YEAR-END OPTION VALUES





                                                 Number of Securities       Value of Unexercised
                                                Underlying Unexercised     In-the-Money Options at
                         Shares                     Options at FY-End                FY-End
                        Acquired      Value    -------------------------   -------------------------
          Name         on Exercise  Realized   Exercisable/Unexercisable   Exercisable/Unexercisable
          ----         -----------  --------   -------------------------   -------------------------
                                                                
William J.  Motto        38,625      $96,261         13,300 /  6,700                $0 / $0
John A.  Kraeutler          -           -           150,973 / 51,100          $319,584 / $46,875
Gerard Blain                -           -            46,210 / 45,000           $35,855 / $10,938
Antonio A.  Interno         -           -           206,568 /  5,250        $1,156,215 / $0
Richard L. Eberly           -           -            12,750 / 15,775            $1,969 / $11,700




                               PERFORMANCE GRAPH

     The  following  graph  shows the  yearly  percentage  change in  Meridian's
cumulative total shareholder  return on its Common Stock as measured by dividing
the  sum  of  (A)  the  cumulative   amount  of  dividends,   assuming  dividend
reinvestment  during  the  periods  presented  and  (B) the  difference  between
Meridian's share price at the end and the beginning of the periods presented; by
the share price at the beginning of the periods presented with the Wilshire 5000
Equity Index,  a New Peer Group Index and an Old Peer Group Index.  The New Peer
Group  consists  of  Biomerica,  Inc.,  Biosite  Diagnostics,  Inc.,  Diagnostic
Products  Corp.,  Hemagen  Diagnostics,  Inc.,  Hycor  Biomedical,  Inc.,  Idexx
Laboratories Corp., Neogen Corp., Quidel Corp., Sybron International and Trinity
Biotech Plc. The Old Peer Group  consists of Diagnostic  Products  Corp.,  Hycor
Biomedical, Inc. and Immucor, Inc.

                COMPARISON OF FIVE YEAR CUMULATIVE TOTAL RETURN*
        AMONG MERIDIAN DIAGNOSTICS, INC., THE WILSHIRE 5000 EQUITY INDEX,
                     A NEW PEER GROUP AND AN OLD PEER GROUP

                                                  New       Old
                                 Meridian         Peer      Peer        Wilshire
                              Diagnotics, Inc.    Group     Group        5000
                              ----------------    -----     -----       --------

SEP-94                             100             100       100           100
SEP-95                             159             162       163           129
SEP-96                             267             198       155           153
SEP-97                             242             173       128           212
SEP-98                             158             164       115           219
SEP-99                             171             194       121           278





SHAREHOLDER PROPOSALS FOR NEXT YEAR

     The  deadline  for  shareholder  proposals  to be  included  in  the  Proxy
Statement for next year's meeting is August 18, 2000.

     The form of Proxy  for this  meeting  grants  authority  to the  designated
proxies to vote in their  discretion on any matters that come before the meeting
except those set forth in the Company's  Proxy  Statement and except for matters
as to which  adequate  notice  is  received.  In order for a notice to be deemed
adequate for the 2001 Annual Shareholders' Meeting, it must be received prior to
November 3, 2000.  If there is a change in the  anticipated  date of next year's
annual  meeting or these  deadlines by more than 30 days,  we will notify you of
this change through our Form 10-Q filings.

QUESTIONS?

     If you have questions or need more  information  about the annual  meeting,
write to:

         Gerard Blain, Secretary
         Meridian Diagnostics, Inc.
         3471 River Hills Drive
         Cincinnati, Ohio 45244

         or call us at (513) 271-3700.

     For  information  about  your  record  holdings  call the Fifth  Third Bank
Shareholder Services at 1-800-837-2755.





                           MERIDIAN DIAGNOSTICS, INC.

               The  undersigned  hereby  appoints  WILLIAM  J.  MOTTO and GERARD
   PROXY       BLAIN, or either of them,  proxies of the undersigned,  each with
    FOR        the power of substitution,  to vote cumulatively or otherwise all
  ANNUAL       shares of Common Stock which the undersigned would be entitled to
  MEETING      vote on the matters  specified below and in their discretion with
               respect to such other  business as may  properly  come before the
               Annual Meeting of Shareholders of Meridian  Diagnostics,  Inc. to
               be held on  January  20,  2000 at 3:00 P.M.  Eastern  Time at The
               Phoenix, 812 Race Street, Cincinnati,  Ohio or any adjournment of
               such Annual Meeting.

     THE BOARD OF DIRECTORS RECOMMENDS A VOTE "FOR" THE FOLLOWING PROPOSALS:

     1.   Authority to elect as directors the five nominees listed below.

          FOR _______                          WITHHOLD AUTHORITY _______

          JAMES A. BUZARD, JOHN A. KRAEUTLER,  GARY P. KREIDER, WILLIAM J. MOTTO
          AND ROBERT J. READY

          WRITE  THE  NAME  OF ANY  NOMINEE(S)  FOR  WHOM  AUTHORITY  TO VOTE IS
          WITHHELD

     2.   Ratification  of the appointment of Arthur Andersen LLP as independent
          public accountants for fiscal 2000.

          FOR _______              AGAINST_______                ABSTAIN _______

          THIS  PROXY  WILL BE VOTED AS  RECOMMENDED  BY THE BOARD OF  DIRECTORS
          UNLESS A CONTRARY CHOICE IS SPECIFIED.


        (This proxy is continued and is to be signed on the reverse side)










                                        Date
                                            ---------------------------, -------


                                        ----------------------------------------


                                        ----------------------------------------

                                        Important:   Please sign exactly as name
                                        appears hereon indicating, where proper,
                                        official  position  or    representative
                                        capacity.  In the case of joint holders,
                                        all should sign.)


          THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS