The objective of this project was to determine the origin of the salts in the saline lakes of the dry valleys by measuring the isotope composition of strontium in lake water, glacial meltwater and soils. The data indicated clearly that the bulk of the strontium in Lake Vanda could not have been derived from a volcanic or marine source. Instead it suggests that the strontium and perhaps also other elements in the water were derived primarily by chemical weathering of the exposed rock in the Wright Valley.