Statistical summaries of surface-water-quality data for 47 streams in Oklahoma have been compiled. Data for the period of record through the 1975 water year at each site were used to develop regression equations for specific conductance-constituent relationships for calcium, magnesium, sodium, sodium plus potassium, bicarbonate, sulfate, chloride, silica, and dissolved solids. Minimum, mean, and maximum values for selected constituents were tabulated for the period of record through the 1975 water year and for individual water years.