Enteric viruses have emerged as important causes of major waterborne disease outbreaks in recent years. The occurrence of enteric viruses in aquatic environments constitutes a major health hazard because of their low infective dose and resistance to environmental breakdown. Currently, our knowledge on the occurrence of enteric viruses in tropical water environments is limited. This thesis describes the first study of the prevalence and molecular characterization of waterborne pathogenic viruses in urban water catchments and community wastewaters in Singapore. Noroviruses were determined to be the most prevalent enteric viruses detected in both wastewater and surface water samples. Molecular characterization revealed the genetic diversity of astroviruses, enteroviruses and noroviruses in water environments. The norovirus strains detected in environmental samples were closely related to the concurrently identified clinical strains in Singapore during gastroenteritis outbreaks between August 2006 to January 2007. Knowledge on the occurrence of human enteric viruses in water environments contributes to the understanding of the mechanisms of viral transmission and the possible role played by water as a vehicle of transmission.