This article presents data on the chemical composition of waters of 12 salt lakes of the Yevpatoria group on the Crimean Peninsula. The geomorphological and geological–hydrogeological features of these lakes are brief ly described. Indices of water saturation with calcium and magnesium carbonates, gypsum, and halite have been calculated by physicochemical modeling. The indices have also been calculated for the 1965 data, which made it possible to track changes in the degree of saturation of the lake waters over the 50-year period. The inf luence of human activity has significantly inf luenced (in contrast to climate f luctuations) the ecosystems of the Crimean salt lakes. This is especially evident in the transformation of the chemical compo- sition of Lake Kyzyl-Yar and less reflected on the state of Lake Bogaily.