Inadequate drinking water and sanitation are amongst the world's causes of prventable morbidity and mortality. This book provides a state-of-the-art review on approaches and methods used in assessing the microbial safety of drinking water. It supports the rapidly emerging trend towards preventive management and a broader, system-wide outlook. It supports a framework for water safety which extends from resource to consumer and is based on rigorous risk assessment and risk management. the book offers guidance on the selection and use of available indicators alongside operational monitoring to meet specific information needs. It looks at potential applications of "new" technologies and emerging methods. This book, which is the outcome fo a shared WHO-OECD initiative since 1998 provides, important background for the development of the third edition of the WHO guidelines for "Drinking Water Quality" and provides information and guidance towards implementation of effective national and local approaches to drinking water safety based on them.