Using a laser monitoring observation technique, the solubilities of paroxetine hydrochloride hemi-hydrate in (water + acetone) were determined by the synthetic method from (294.45 to 323.20) K, respectively. Results of these measurements were correlated by the three variants of the combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) model. For the seven group data studied, three variants of the (CNIBS/R-K) equation were found to provide accurate mathematical representations of the experimental data and variant 2 is the best of the three variants. (c) 2004 Elsevier Ltd. All rights reserved.