In this paper, the results of mercury concentrations in two abiotic compartments (river and suspended particles) and two biotic compartments (fish and human hair) from the upper Madeira rivers of the Bolivian Amazon basin are presented. Because of the local hydrological regimes and a high deposition rate in the plain, due to the presence of a subsidence zone at the bottom of the Andean piedmont, in the dry season, the highest mercury concentrations and fluxes were not found in rivers where mining activities took place (2.25-6.99 ng l-1; and 1.07-8.67 mg Hg d-1 km-2), but at the outlet of the Andean basins exploited for their alluvial gold (7.22-8.22 ng l-1; and 9.47-9.52 mg Hg d-1 km-2). The total mercury concentrations measured in surface waters of the upper Beni basin varied during the dry season, from 2.24 to 2.57 ng l-1 in the glacial waters of the Zongo river, to 7.00 ng l-1 in the Madeira River at Porto Velho and 9.49-10.86 ng l-1 at its confluence with the Amazon. The results obtained from fish indicate, on one hand, that 86% of the piscivorous fishes collected in the Beni river were contaminated, and, on the other hand, their high mercury concentrations could exceed by almos four times the WHO (1976) safety limit. (Résumé d'auteur)