The purpose of this work is to study the dissolution behavior of lapatinib ditosylate (LB-DT) in different solvents and determine the suitable solvent and composition to improve dissolving capacity. In selected pure organic solvents, LB-DT exists in the form of anhydrous. The largest solubility data was found in acetone and lowest in toluene at the determined temperature, and it decreases as the following order: acetone > tetrahydrofuran (THF) > acetonitrile > n-propanol > isopropanol > 1-butanol > ethyl acetate > toluene. While in mixture of THE aqueous, it exist the form of monohydrate, and the solubility increases at first and then decreases with the increasing mass fraction of THF. The composition dependence of the solubility has a maximum around w = 0.6 at all investigated temperatures. The (KAT-LSER) model was applied to analyze the effect of the solute-solvent intermolecular interactions on the solubility in pure organic solvents. A series of models based on solubility parameter and the solid-liquid equilibrium equation were employed to provide insight to data. In the following, the analysis of apparent thermodynamic properties indicates that the dissolution process is apparently not only endothermic but also entropy-driving. (C) 2019 Published by Elsevier B.V.