New solubility data for methane, carbon dioxide, and their binary mixtures in pure water were obtained at 344.25 K and from 10 to 100 MPa. A thermodynamic model that combines a cubic equation of state (Peng-Robinson with k(ij) given in the literature) with the Henry＇s law approach has been elaborated. It has been shown that the (P,T) functional form of Henry＇s constant given by the Krichevsky-Kasarnovsky equation is applicable. It involves two important parameters: partial molar volume at infinite dilution and Henry＇s constant at the vapor pressure of water. Neither of these two parameters is a function of pressure or composition. The Henry＇s constant correlations of Li and Nghiem and Harvey, and the partial molar volume correlation of Lyckman et al. have been validated using a great number of solubility data.