Drinking water quality and the presence of natural arsenic (As) were studied in a rural, less developed area of the southern part of the Poopó lake basin in the Central Bolivian Altiplano. People in this area use untreated surface- and ground-water directly as drinking water. Water is extracted from excavated wells and from few rivers occasionally present during the rainy season. Forty-one wells and seven different sites along four rivers were sampled as they are common sources for drinking water. The main characteristics of the sampled waters showed a slightly alkaline pH, high electrical conductivity and high salinity where the principal components were sodium, chloride and bicarbonate. Arsenic concentrations reached values up to 623 μg L -1 exceeding the current WHO guideline value (10 μg L -1) in all rivers and in ninety-five percent of the sampled wells. Heavy metals and other trace elements showed relatively low concentrations.