The thermodynamics of solid-liquid equilibrium is applied to binary systems including a semicrystalline polymer and a solvent. Group-contribution activity coefficient models are used for describing the nonideal behavior of the liquid phase. The solid polymer properties are obtained via group-contribution methods and tested for consistency. Methods for the simultaneous solution of the solid-liquid and liquid-liquid equilibrium are presented. The full phase envelope of polymer solutions can be predicted, and the use of the empirical solubility parameter approach is avoided. The effects of polymer semicrystallinity and molecular weight on the solid-liquid equilibria are displayed, and a comparison of our predictions with experimental data is performed.