In assessing exposure to indoor air contaminants, the understanding of population water-use behavior for indoor water-use activities as a function of demographic characteristics is vital to obtaining realistic exposure estimates. In response to the need for more specific and usable population based water-use data for exposure modeling, new data sources have been analyzed. Frequencies, durations, volumes and flowrates of showers, baths, clothes washers, dishwashers, toilets and faucets are presented, derived from analyses of the National Human Activities Pattern Survey (NHAPS) database, the Residential End Uses of Water Study (REUWS) database, the Residential Energy Consumption Survey (RECS) as well as from current literature and manufacturer information. Distribution parameters for water use behaviors are identified for use as inputs for modeling exposure to water borne contaminants. The work has been funded wholly or in part by the United States Environmental Protection Agency and has been approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.