During late October 1977, water discharge from Minidoka Dam into the Milner reach of the Snake River was less than 22 cubic meters per second, compared to normal flows for that time of year of about 42 cubic meters per second or more. To determine if impaired water-quality conditions existed, samples were collected at several sites above and below major point-source waste discharges near Burley, Idaho. Data collected for this study indicate some water-quality impairment within the study reach. At site 15 near Milner Dam, dissolved oxygen was below the 90-percent saturation standard prescribed by the Idaho water-quality standards. The total coliform and fecal coliform standards were exceeded at about one-third of the sites sampled on the main stem of the Snake River. Un-ionized ammonia concentration exceeded U.S. Environmental Protection Agency water-quality criteria at one site near Burley. Concentrations of trace metals, insecticides, and herbicides were all low; none exceeded existing criteria.