Mercury contamination caused by the amalgamation of gold in small-scale gold mining is an environmental problem of increasing concern, particularly in tropical regions like the Amazon, where a new boom of such gold mining started in the 1970s. In Brazil, research into these problems has been carried out for many years, but there is no available data for Bolivia. The present paper surveys mercury contamination of a Bolivian river system in the Amazon drainage basin, measured in water, fish, and human hair. High concentrations in fish and human hair from consumers of carnivorous fish species are reported. The potential health risk from fish consumption was evident in people living downstream of gold-mining activities, but not in the mining population itself.