Nutrient (phosphorus) concentration in Swiss lakes has considerably increased between 1950 and 1975, and has thereafter decreased due to effective water pollution control measures. The aims for lake restoration from a limnological and a fish biological point of view are presented and discussed, using case histories from four lakes. The four examples illustrate the lack of agreement between expectations from the public regarding the effect of lake restoration measures on fish stocks on one hand, and the true evolution on the other: Some eutrophic («sick») lakes are the most productive salmonid lakes today, while re-oligotrophicated («healthy») lakes are showing signs of collapse of the fishing yield. These apparent contradictions are explained by man 's actions of stocking juvenile coregonids in eutrophic lakes, and by the decreasing productivity of today 's oligotrophic lakes. In order to optimize fishery and lake restoration objectives, long-term total phosphorus concentration should be between about 10 and 30 μg/I: Above 30-40 μg/I total phosphorus, natural reproduction of salmonids (coregonids, Arctic char) is jeopardized, while below 10 μg/I fishing yield potential is low. For ecological considerations, and because it will hardly be feasible to stabilize lake phosphorus concentration within the proposed range, phosphorus concentration should be kept as low as possible. Apart from complying with most of the fisheries interests, low phosphorus concentrations are in line with other, more important objectives of lake use, e.g. for drinking water or recreation.