Abstract: The discharge-weighted average concentrations of dissolved solids, chloride, and sulfate for many of the principal streams in Texas are less than 500 mg/1 (milligrams per liter), 250 mg/1, and·250 mg/1, respectively. At 65 of 131 sites on streams that were sampled at least 10 times, the biochemical oxygen demand of at· least half the samples exceeded 3,0 mg/1. At 20 of the sites, the dissolved-oxygen content of at least !half the samples was less than 5.0_ mg/1. The higher concentrations of minor elements usually were detected in waters from urban areas, indicating a relation to man's activities. Small amounts of some pesticides are widely distributed in low concentrations. The higher concentrations usually were detected in waters from urban areas. Small amounts of some of the pesticides studied are widely distributed in surface waters in Texas. Some of the more widely distributed pesticides were 2,4,5-T at 96 sites, diazinon at 80 sites, 2,4-D at 78 sites, dieldrin at 77 sites, Silvex at 47 sites, DDT at 67 sites, lindane at 59 sites, DDD at 51 sites, DDE at SO sites, and chlordane at 38 sites.