Knowledge of the solubility of water in hydrocarbon fluids is essential for the design, simulation, and optimization of thermal oil recovery processes. This study proposes the use of cubic-plus-association equation of state (CPA-EoS) to predict the mole fraction of water in hydrocarbon fluids with specific gravity and molecular weight as the correlating parameters. Experimental data for water solubility in petroleum fractions, heavy oils, and bitumens was represented with an absolute average relative deviation (AARD) of less than 6.8%. The binary interaction parameter between the water and hydrocarbons was determined for different crudes. The proposed model can be applied to petroleum fractions, heavy oils, and bitumens with molecular weights between 140 and 678 g/mol at temperatures up to 560 K, which is the practical range of many industrial applications. (C) 2015 Elsevier Ltd. All rights reserved.