At the Otjihase mine a stratiform massive sulphide mineralization occurs, which is associated with the Matchless Amphibolite Belt. Main ore minerals in the deposit are chalcopyrite and pyrite, with only chalcopyrite being of economic importance. The pyrite dumped in the tailings dump generates acid mine drainage. The aim of the study was to investigate the effects of mining and ore processing on the environment. This was achieved by detailed geochemical investigation of the tailings impoundment, stream sediments, soil and water samples. The samples were analysed for Cu, Zn, Cd, Pb, As and other metals. The results were then compared to regional background values, as well as international soil and water guidelines to assess potential pollution from the mining activities. It became obvious that mining and processing activities at Otjihase, with subsequent disposal of waste rock and tailings, causes significant contamination of stream sediments and surface water. The river system is characterised by elevated copper, zinc, cobalt and chromium contents in both stream sediments and surface water. The main source of contamination is tailings dump (11 million m3 of material). The seepage from the tailings dump and the pyrite stockpiles are highly acidic (pH2) and saline.