On June 21, 2011, the Food and Drug Administration (FDA) published a proposed rule that would amend current sterility test requirements for biological products to provide manufacturers with greater flexibility and to encourage use of the most appropriate and state-of-the-art test methods for assuring the safety of biologicals. Comments on the proposed rule are due by September 19, 2011. The most significant proposed changes to current regulations governing sterility testing include the following: (i) elimination of specified sterility test methods, culture media formulae, and culture media test requirements; (ii) elimination of specified membrane filtration procedure requirement for certain products; (iii) elimination of specified sterility test requirements for most bulk material; (iv) modification of the repeat sterility test requirements (repeat tests would occur only once for each lot and would be limited to situations where the quality control unit conclusively determines that the contamination is the result of laboratory error or faulty materials used in conducting the sterility test); (v) replacement of the storage and maintenance requirements for cultures of test organisms used to determine the ‘‘growth-promoting qualities’’ of culture media with (a) validation requirements specifying that any sterility test used is able to consistently detect the presence of viable contaminating microorganisms and (b) verification of “growth-promoting properties” or microorganism-detection capabilities of test and test components; (vi) replacement of the sample size or amount requirement with a requirement that the sample be appropriate to the material being tested; and (vii) replacement of the current “Interpretation of test results" paragraph under § 610.12(c) with a requirement that manufacturers establish, implement, and follow written procedures for sterility testing that describe, at a minimum, the test method used, the method of sampling, and the written specifications for acceptance or rejection of each lot. FDA is specifically seeking public comment on whether the phrase "growth-promoting properties," rather than "growth-promoting qualities" is more appropriate terminology within the regulations. FDA also requests comments on whether the proposed testing validation requirements are sufficient to ensure adequate validation of novel sterility test methods, whether the current exceptions to the sterility test requirement should be changed, and the frequency with which manufacturers diverge from the retesting protocol and the costs that limiting retests will impose.