Comprehensive planning for water resources development and use in Oklahoma requires a historical perspective on water resources. The U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, summarized the 1950-2005 water-use information for Oklahoma. This report presents 1950-2005 estimates of freshwater withdrawal for water use in Oklahoma by source and category in 5-year intervals. Withdrawal source was either surface water or groundwater. Withdrawal categories include: public supply, irrigation, livestock and aquaculture, thermoelectric-power generation (cooling water), domestic and commercial, and industrial and mining. Withdrawal data were aggregated and tabulated by county, major river basin, and principal aquifer. The purpose of this report is to summarize water-use data in Oklahoma through: (1) presentation of detailed information on freshwater withdrawals by source, county, major river basin, and principal aquifer for 2005; (2) comparison of water use by source, category, major river basin, and principal aquifer at 5-year intervals from 1990-2005; and (3) comparison of water use on a statewide basis by source and category at 5-year intervals from 1950-2005. Total withdrawals from surface-water and groundwater sources during 2005 were 1,559 million gallons per day-989 million gallons a day or 63 percent from surface-water sources and 570 million gallons per day or 37 percent from groundwater sources. The three largest water use categories were: public supply, 646 million gallons per day or 41 percent of total withdrawals; irrigation, 495 million gallons per day or 32 percent of total withdrawals; and livestock and aquaculture, 181 million gallons per day or 12 percent of total withdrawals. All other categories were 237 million gallons per day or 15 percent of total withdrawals. The influence of public supply on the total withdrawals can be seen in the eastern two-thirds of Oklahoma; whereas, the influence of irrigation on total withdrawals can be seen in the western third of Oklahoma. Surface-water sources were dominant in the eastern half of Oklahoma and groundwater sources were dominant in the western half of Oklahoma. Public supply withdrawals increased steadily from 1990-2000 and then decreased slightly in 2005, mainly because of a decrease in surface-water withdrawals. Irrigation withdrawals increased from 1990-1995 and then decreased steadily to 2005. Total livestock and aquaculture withdrawals steadily increased from 1990-2005. The largest increase in the other categories was for thermoelectric power generation that has steadily increased and almost doubled from 1990-2005. Surface-water sources have been increasing in importance from 1950-2005, in part because of the increasing percentage of surface-water for public supply as the total population of Oklahoma and population served by surface-water sources increased. Groundwater sources have been generally decreasing in importance as a percentage of total withdrawals in recent years. However, the magnitude of groundwater withdrawals was greatly dependent on irrigation withdrawals and specifically irrigated acreage in the panhandle.