The claim for adequate characterization of the starting materials in the form of special files called Drug Master Files (DMFs) is a GMP aspect which in recent years has clearly dominated the disussion on further improvements of the quality and safety of drug substances which is to be ensured by registration and inspection. Those files become necessary when supplementary information is required to prove that the information on the control methods and the results analytical test are suitable to allow satisfactory description and specification of the of the drug substance used. In October 1991 the International Association for Pharmaceutical Technology (APV) and the International Pharmaceutical Federation (F.I.P.) organized a symposium on "Drug Master Files: Global Harmonization of Quality Standards". The lectures given at this event provided the basis for the present paperback.