During 1990, about 1,460 million gallons per day (Mgal/d) of freshwater was withdrawn from surface- water and ground-water sources in Maryland. Total freshwater withdrawals increased during 1991 to about 1,500 Mgal/d. Saline surface-water withdrawals for cooling condensors increased from about 4,550 Mgal/d during 1990 to 5,760 Mgal/d during 1991. During 1990-91, most freshwater withdrawals (about 1,220 Mgal/d during 1990 and 1,250 Mgal/d during 1991) were from surface-water sources. More than 70 percent of the fresh surface water was withdrawn and used in the Potomac drainage basin. Most ground water (about 170 Mgal/d in 1990 and 184 Mgal/d in 1991) was withdrawn and used in the Upper Chesapeake drainage basin. The Potomac Group aquifers provided most of the ground water (about 64 Mgal/d during 1990 and 68 Mgal/d during 1991 or about 27 percent each year). Ten water-use categories represent the major demands on the surface-water and ground-water resources of the State: Public supply, domestic, commercial, industrial, mining, thermoelectric power, hydroelectric power, livestock, irrigation, and aquaculture. Largest withdrawals were for public supply (798 Mgal/d during 1990 and 826 Mgal/d during 1991), and the water was used by residences, commercial establishments, and industries. Baltimore City received the largest public-supply deliveries (totaling about 135 Mgal/d during 1990 and 127 Mgal/d during 1991). Freshwater withdrawals for self-supplied domestic use, aquaculture, and irrigation increased during the period, whereas withdrawals for commercial, industrial, thermo- electric power, and mining uses decreased.