We use output from global climate change simulations with seven Atmosphere-Ocean General Circulation Models (AOGCMs) to assess possible changes in Caspian Sea basin hydrologic budget and corresponding changes in the Caspian Sea Level (CSL) for the 21st century under different greenhouse gas (GHG) emission scenarios (A1b and A2). Although most models project an increase in precipitation over the Volga river basin, where most of the runoff into the Caspian Sea is generated, a steady decline in the CSL is mostly estimated. This is due to large increases in evapotranspiration over land and over the Caspian Sea surface. By the end of the 21st century, the ensemble average of the model-based estimates suggest a 9 meter drop in the CSL for both scenarios analyzed. This could be potentially devastating for the surrounding region if no adaptation or mitigation measures are taken.