Improving the efficiency of water utilities and reducing water losses are becoming top priorities in Asia, with its often-limited water resources and rapidly increasing urban population. This publication provides an up-to-date introduction to the subject matter, highlights the complexity of managing non-revenue water (NRW), offers guidance on NRW assessment, and recommends appropriate performance indicators. It is, to a large extent, based on the work of the Water Loss Specialist Group of the International Water Association in the last decade, and is amply complemented by the authors' practical experiences in Asia and in other countries around the world.