Maintenance can impact both the quality of products and the compliance of pharmaceutical processes. Maintenance programs have long been recognized as critical to the success of the operations they support. This Guide is focused on maintenance in GMP areas and provides a practical and consistent interpretation of the necessary elements of a pharmaceutical maintenance program. Since the first edition of this Guide, the ICH Q9 risk-based approach has been widely adopted worldwide. This edition reflects alignment with the risk-based approach with respect to maintenance and the pharmaceutical industry as a whole. Updates to this edition include consolidating basic and good practice categories, adding clarification on terminology for users, and updating examples.