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                                    EXHIBIT 3

                         FORM OF LETTER TO STOCKHOLDERS

Dear Stockholder:

         On December 11, 1996, your Board of Directors adopted a stockholder
rights plan in an effort to assure that all Quidel Corporation stockholders
receive maximum value in the event of an attempted or actual takeover of the
Company. We have enclosed a summary description of the plan, which we urge you
to read carefully.

         Adoption of rights plans is a common practice among public companies in
the United States. Rights plans are intended to provide the Board of Directors
with additional time and bargaining power to protect stockholder interests in
the event of an unsolicited takeover bid. Quidel's rights plan will not prevent
a takeover of the Company on terms that are in the best interests of all
stockholders. However, the rights plan should encourage a potential acquiror to
negotiate with the Board prior to attempting a takeover. This should position
the Board to protect your interests.

         The Quidel rights plan involves distribution of one "Right" for each
share of common stock outstanding on January 10, 1997. Thereafter, each newly
issued share of common stock will also include a Right. Initially, there will be
no separate Rights certificates. Instead, each Right will simply be a part of
the share of common stock to which it is attached. It will be represented by the
common stock certificate, it will trade automatically with the common stock, and
it will not be separable or exercisable unless certain events occur.

         If a person or group acquires 15% or more of Quidel's outstanding
common stock, each Right not owned by the acquiror or its affiliates will
entitle its holder to pay the Company $24 (the exercise price per Right) and
receive newly issued shares of common stock worth $48. For example, if the stock
were trading at $12, each Right would entitle its holder to purchase 4 shares
for $24, or $6 per share. This ability of stockholders other than the acquiror
to purchase additional shares at a 50% discount from market would cause an
unapproved takeover to be much more expensive to an acquiror. As a result, a
potential acquiror would have a strong incentive not to pursue a hostile
strategy, and instead to negotiate with your Board of Directors to redeem the
Rights or approve the transaction so that the Rights do not become exercisable.

         Adoption of the rights plan does not affect the financial strength of
the Company and will not interfere with our business strategy and plans. The
issuance of the Rights alone will not affect earnings per share or change the
way in which you can presently trade the Company's shares.

         The attached summary describes the Rights in more detail. Thank you for
your continued support of Quidel Corporation.

Sincerely,