The gap between the sophisticated Non-Revenue Water (NRW) reduction programs in well managed water utilities and the situation in many of the world's water utilities (and especially in utilities in developing countries) is widening at a fast pace. In the last decade a comprehensive set of analytical tools, water loss reduction strategies and specialized equipment has been developed. The work of the International Water Association (IWA) Operation and Maintenance Specialist Group in general, and its Water Loss Task Force in particular, has led to a set of performance indicators ideally suited to assess the water loss situation and to quantify the components of NRW. This paper outlines a basic NRW reduction strategy and is intended to motivate utility managers to establish a standard water balance, calculate the level of NRW, quantify its components and identify main problem areas. Part one of this paper deals with the tasks required to investigate and assess the components of non-revenue water (NRW). This is a necessary first step in a diagnostic approach to understanding the condition of the network, the way it is operated, and the constraints acting upon it. The second part of the paper deals with the tasks and tools required to address the constraints, and to develop a strategy to reduce NRW which is practicable and achievable, and which can be adapted for any distribution network anywhere in the world. Includes 8 references, tables, figures.