This document introduces the Guide to Good Manufacturing Practice for Medicinal Products published by the Pharmaceutical Inspection Co-operation Scheme (PIC/S). It provides a brief history of the development of the guide from its origins in the WHO GMP guide. It explains that the PIC/S GMP guide and the EU GMP guide have been developed in parallel and are practically identical, with some minor differences explained. It also introduces Part II of the PIC/S GMP guide which covers GMP for active pharmaceutical ingredients and was originally developed by the International Conference on Harmonisation. Finally, it provides information on the adoption and revision history of the current PIC/S GMP guide.