This International Standard specifies a procedure to be used in evaluating the antimicrobial preservative activity of all preserved multidose contact lens care products, and provides guidance on methods to be used for determination of discard date as informative annexes. This test is applicable to products for up to a 28-day discard date. The test is not applicable to sterile products packaged in unit doses for single use or multidose containers designed with physical barriers to microbial contamination (e.g. aerosol containers). NOTE 1 Principles of the test may be used to extend discard dating beyond 28 days. See annexes B, C, D and E. NOTE 2 Use of multiple or mixed microbial challenges and/or inclusion of contact lenses or other organic load can influence the apparent antimicrobial activity of a particular product. The evaluation of these variables together with testing against a larger panel of microorganisms and testing of samples from partially used containers may be of value in developing a contact lens care product, but are excluded from the scope of this International Standard.