IntroductionThe EU Rules for Manufacture of Medicinal Products GMP, published in 1989, contained an annex on the manufacture of sterile medicinal products to ensure the sterility of medicinal products. A version of this annex, “Annex 1”, issued according to its document history in May 2003, underwent several targeted updates in the interim period until 2009, but now Annex 1 has undergone, for the first time, a complete revision.The new version of Annex 1, released on 22 Aug 2022, is a comprehensive revision to the previous Guideline, which covers all aspects related to the facilities, utilities, equipment, and systems and controls used for the production of sterile medicinal products. This includes sections on aseptic preparation and processing, and Aseptic Process Simulation (APS), and media fill. There is much interest regarding additions to this latest revision of Annex 1, which has much more detail compared to previous versions. In this article, we have reviewed the section on Aseptic Process Simulation (APS), which previously consisted of five brief paragraphs, and now consists of four pages– approximately a 300% increase in the content related to APS. Drawing on our recent publications regarding the application of media simulations in the validation of aseptic processes,2,3 this article aims to assess the changes and additional requirements related to APS.