By using a laser monitoring observation technique, the solubilities of Lansoprazole in ten pure solvents as well as in a binary solvent mixture (isopropyl alcohol) were measured in the temperature ranging from 283.15 to 318.15 K. The experimental data were fitted using the modified Apelblat equation and two variants of the combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) model. The models were proven to give good representations of the experimental data. Computational results showed that variant 2 was superior to the variant 1 after comparison between the two variants of CNIBS/R-K model. The solubility enthalpy and entropy of Lansoprazole in all pure solvents and the mixed solvent system were calculated using van't Hoff equation. The dissolving process was endothermic and entropy-driving. (C) 2012 Elsevier B.V. All rights reserved.