The quality of water in Lake Peipus (Pskov-Chudskoye) is described according to data from long-term monitoring. The lake tends to be of the eutrophic type, with turbid water and oxygen deficiency in near-bottom water layers during winter and summer stagnation. Permissible nutrient loadings on the lake were defined according to its assimilating capacity. Current phosphorus and nitrogen loadings are above the permissible levels, and P and N supply from point and non-point sources needs to be reduced.