This publication provides guidance on high standard chemistry programmes in accordance with plant safety policy and the regulatory requirements. It will also be useful to corporate managers and other staff responsible for supporting or monitoring plant activities and oversight of plant chemistry programme implementation, as well as to regulatory authorities and relevant nuclear power organizations. The publication elaborates on the requirements established in IAEA Safety Standards Series No. NS-R-2, Safety of Nuclear Power Plants: Operation. Contents: 1. Introduction; 2. Functions, responsibilities and interfaces; 3. Chemistry programme; 4. Chemistry control; 5. Chemistry aspects of radiation exposure optimization; 6. Chemistry surveillance; 7. Management of chemistry data; 8. Training and qualification; 9. Quality control of chemicals and other substances.