Modeling the solubilities of fatty acids is important because these compounds are used in various industries. In this work, a thermodynamic model based on Redlich-Kwong equation of state with Kwak-Mansoori mixing rules was used to model the solubilities of fatty acids in supercritical carbon dioxide. The model uses only one adjustable parameter and this parameter varies linearly with the chain length of the fatty acid. Therefore, this model can be potentially used to predict the solubilities of various fatty acids in supercritical carbon dioxide. © 2004 Elsevier B.V. All rights reserved.