An apparatus for measuring the solubility of gases in aqueous electrolyte solutions under high pressure and elevated temperature conditions is described. The solubility of methane, carbon dioxide, nitrogen, and a natural gas mixture in aqueous sodium bicarbonate solutions were measured up to 58 MPa and 403 K. The modified Patel-Teja equation of state proposed by Zuo and Guo (1991) for aqueous electrolyte systems was applied to correlate the measured solubility data, and satisfactory results were obtained.