Water and steam may be used in the manufacture of products, cleaning operations, and laboratory activities within pharmaceutical or biopharmaceutical operations. Systems that generate and distribute water and steam that may come into contact with product/or process contact suraces, or that are used in the testing of product, are subject to commissioning and qualification (verification) practices. This second edition of the ISPE Good Practice Guide: Approaches to Commissioning and Qualification of Pharmaceutical Water and Steam Systems, discusses practices and activities associated with the commissioning and qualification (verification) of pharmaceutical water and steam systems. The guide focuses on items which directly affect quality attributes of water or steam during production, storage, and distribution. both High Purity Water and Pure (Clean) Steam are considered and information on other types of pharmaceutical water and steam is also provided. This Guide can be used by industry professionals involved in the design, construction, commissioning, and qualification of new or newly renovated water and steam systems, which are regulated by the international healthcare authorities. It addresses compliance with international regulations and guidelines for water and steam systems, and considers new systems, extensions to existing systems, and existing validated systems.