Water-use data were compiled for the 78 municipios of the Commonwealth of Puerto Rico for 2000. Five offstream categories were considered: public-supply water withdrawals, domestic self-supplied water use, industrial self-supplied withdrawals, crop irrigation water use, and thermoelectric power fresh water use. Two additional categories also were considered: power generation instream use and public wastewater treatment return-flows. Fresh water withdrawals for offstream use from surface- and ground-water sources in Puerto Rico were estimated at 617 million gallons per day. The largest amount of fresh water withdrawn was by public-supply water facilities and was estimated at 540 million gallons per day. Fresh surface- and ground-water withdrawals by domestic self-supplied users was estimated at 2 million gallons per day and the industrial self-supplied withdrawals were estimated at 9.5 million gallons per day. Withdrawals for crop irrigation purposes were estimated at 64 million gallons per day, or approximately 10 percent of all offstream fresh water withdrawals. Saline instream surface-water withdrawals for cooling purposes by thermoelectric power facilities was estimated at 2,191 million gallons per day, and instream fresh water withdrawals by hydroelectric facilities at 171 million gallons per day. Total discharge from public wastewater treatment facilities was estimated at 211 million gallons per day.