Using existing Nevada State drinking-water standards as a measure of the overall water quality, ground-water quality in principal aquifers of the upper Carson River basin is generally excellent. Ground-water quality in the Carson Desert, the distal end of the Carson River basin, displays extremes in concentrations of major and minor inorganic constituents, with dissolved solids reaching concentrations exceeding sea water. More than 10 percent of sampled ground water in the principal aquifers contain concentrations of arsenic, dissolved solids, and manganese greater than the drinking-water standards. Nearly all sampled ground water in the basin had radon-222 activities greater than the proposed Federal maximum contaminant level of 300 picocuries per liter. Uranium concentrations greater than the proposed Federal maximum contaminant level of 20 micrograms per liter were found in ground water in the adjacent Sierra Nevada.