The preservative efficacy test is a test method that is used to evaluate microbiological product stability (preservative efficacy).The performance of such test is also part of the legal requirements to prove the adequate microbiological quality and product safety of cosmetic products.

It must, however, be emphasised that the efficacy statement provided in such tests cannot be seen as a proof of microbiological product safety. Historical data show that attempts to improve the validity of the efficacy statement by changing the test method or the required death kinetics have been disappointing. This paper describes a method that can lead to an improved efficacy statement.