Sediment samples from the main Swiss rivers and lakes were analyzed in 1973-1975 to evaluate their heavy metal content. Strong Hg contamination was found in lac Leman and its main tributary, the Rhone river. Weaker contamination was found in lac de Joux and lac de Morat. Apart from Hg, the other pollutants include chromium, zinc, cobalt, copper, tin and cadmium, with lead as an accessory. This study has led to the localization of the main anthropogenic sources of heavy metals to Swiss lakes and rivers.