The particulate matter cycle in Lac Léman (Switzerland) was studied by means of suspended solid, trap and bottom sediment collection. Major oxides, trace elements and nutrients were analyzed, and concentration as well as sedimentation rates measured. Epilimnetic production of calcium carbonate, biogenic silica, organic matter and silicates was estimated from chemical composition changes in water, and decomposition rates calculated. Use of a simple model based on a "Flux = concentration * transfer velocity" relation shows the occurrence of hypolimnetic sources for silicates, Ca, organic C, Mn, Zn and Cd.