With the assistance of massbalances nitrogen (N) elimination rates in various Swiss lakes were estimated during the last 20 years. The results show that 10000-15000t of N are annually eliminated by the Swiss lakes thus reducing the N export with the rivers Rhine, Rhone, Ticino, Poschiavino and Inn by about 10-15 %. Dry years and low oxygen concentrations are the most probable reasons for the distinctive reduction of the average nitrogen concentration in many Swiss lakes between 1987 and 1989. On account of the reduced phosphate concentrations the N elimination performance in the lakes of Central Europe in future will probably be reduced. It will, therefore, become increasingly important to initiate measures that prevent the excessive N discharge into the surface waters.