The EC Cosmetics Regulation demands documented evidence of the microbiological quality and safety of cosmetic products. This includes the performance of a preservation efficacy tests (PET) if methodologically applicable. Various requirements must be observed if the test will be reasonably planned and performed. This does not only mean following respective normative provisions like the ISO 11930 (advised as standard) and performing the test in a qualified way. In fact, further aspects should be respected regarding the extent and the frequency of the test performance to obtain praxis-relevant results. For instance, “praxis-microorganisms” should additionally be used in the test, changes of the formula, of the production method and of the packaging must be regarded for the test performance, and aspects concerning the test feasibility (products falling under ISO 29621) and of the test validity should be considered. The test can only be applied in this sense, if it is handled as part of the microbiological quality management-system (MQM). Only then essential information will be generated, communicated, and respected for the test. Additionally, the system defines necessary processes and measures and provides supplementary evidence for preservation efficacy and product quality.