UNESCO held a Symposium on Frontiers in Urban Water Management in 2001 and the resulting publication proposed the way forward in this challenging field. At a subsequent meeting at UNESCO Headquarters, a programme comprising eight inter-related studies on urban water management was initiated by UNESCO. This report presents results of one of those studies, which focuses on the assessment of anthropogenic impacts on the urban hydrological cycle and the urban environment, including processes and interactions in the urban water cycle. This study was made necessary by the fact that effective management of urban waters should be based on a scientific understanding of anthropogenic impacts on the urban hydrological cycle and the environment. The report is meant to be a guidance manual on anthropogenic alterations of the urban water cycle and the environment, with reference to various climatic zones and potential climate changes.