The methods for quantitatively estimating ground-water discharge to the Baltic Sea and the possibilities of applying these methods to investigations of the role of ground water in the water and salt balances of the Baltic Sea are discussed. The combined hydrological and hydrogeological method, the hydrodynamic method, and the method of the average long-term water balance of recharge areas are recommended for general quantitative estimation of ground-water discharge to the sea. Data on the ground-water discharge to the Baltic Sea from the zone of intensive circulation (relatively shallow aquifers) within the U.S.S.R. are presented. Certain conclusions are drawn, and objectives of future investigations are mentioned.