Water reuse is a fact of life, as is evident in the evaporation and precipitation of the natural water cycle, and human history has many examples of reclamation and reuse.  A recurring theme in water resources and environmental engineering is that improved wastewater treatment provides effluent of such quality that it should not be wasted but put to beneficial use. In the face of growing problems of water shortage and environmental pollution, using reclaimed wastewater as a water resource holds great potential, particularly compared with the cost and environmental impact of seeking to enhance water resources conventionally with dams and reservoirs.  To be successful reuse schemes must be tailored to the local circumstances, based on careful consideration of the economics, public health issues, regulatory framework, aesthetic and social acceptability, in addition to fundamental scientific and engineering aspects.  Such issues featured strongly at the 4th Wastewater Reclamation and Reuse Symposium, and from its large and high-quality programme 44 articles have been peer-reviewed and selected for these proceedings.  In addition to case studies that provide valuable insights into the varied practice of reuse, they address the following topics: management and policy; legislation; agriculture; industrial reuse; urban reuse; disinfection; endocrine disruptors; soil aquifer treatment. The scientific, technical and engineering developments and insights from practical experience reported in these papers provide essential reference material for everyone working towards a more efficient and effective use of reclaimed water, while protecting human health, to cope with ever scarcer water resources for the developed and developing world.