Viruses of animals, plants, and bacteria abound in sewage and receiving waters. Their ecological impact has, for the most part, gone unheeded except as it relates to viruses from human sources. Viruses present at levels infective to man have been recovered from waters used for recreational or drinking purposes. Their presence in a water environment virtually always denotes prior contamination by domestic wastes. Neither conventional sewage treatment processes nor the discharge to land or water of sludges produced by these processes achieve full viral control. Many environmental virologists advocate the setting of permissible virus limits for those recreational and potable waters dominated by wastewater effluents. The initiation of regulatory pressure to restrict virus discharges into these water environments has been instituted in Montgomery County, Maryland, and in the states of California and Arizona.