A modified solution-diffusion model is presented which describes separation of ethanol-water mixtures. The model is particularly useful in predicting the solute (ethanol) flux as the mixture approaches the azeotrope point where ethanol activity is greater than 0.6, Based on the experimental observations obtained from the literature, the model assumes that polymers of about seven molecules of ethanol are formed, which are then transported through the membrane along with water and ethanol monomers and dimers. It is shown that the ethanol flux can be predicted more accurately as compared with the existing model. Comparisons with experimental data from the literature confirms this model.