In this article, the solubility behaviour of budesonide in pure and alcohol-modified subcritical water (SBCW) solutions between 25 degrees C and 200 degrees C is reported. Methanol and ethanol were selected as modifiers. In the presence of ethanol, the solubility of budesonide in SBCW increased up to 10 times. In all reported cases, the solubility of budesonide was directly dependant on the dielectric constant of the solvent mixture. A correlation between the budesonide solubility data and the dielectric constant of SBCW was developed. The correlation parameters were altered to improve the accuracy of the outputs of the solubility model for 9-anthracenemethanol in SBCW. The model was able to predict budesonide solubility in SBCW and SBCW-alcohol solutions with an average error of 3%. The model is applicable to all the budesonide-SBCW-alcohol systems investigated in this work and is valid for a broad range of SBCW ternary systems. The solubility of budesonide was also modelled using the Modified Universal Functional Activity Coefficient (M-UNIFAC) model. Corrections were made to the interaction parameters so that the M-UNIFAC model was able to reproduce the solubility of budesonide in SBCW within 5% of experimental values. In order to check the validity of the parameter correction, the solubility of 9-anthracenemethanol in SBCW was established and modelled. (C) 2010 Elsevier B.V. All rights reserved.