A single layer PDMS membrane was synthesized and gas permeation behavior of ternary gas mixtures consisting of C3H8, CH4 and H-2 through it was investigated. Permeability, solubility and diffusivity of gases were measured at different upstream pressures, feed temperatures and feed compositions. The results showed that, increasing pressure and temperature decreases permeability of more condensable gas, C3H8, while increases that of lighter gases, H-2 and CH4. Solubility of all components in the gas mixture increased with increasing pressure and decreasing temperature. Diffusivity of all components increased with increasing temperature. With increasing pressure that of the lighter gases increased, while diffusivity of the more condensable gas decreased. Increasing C3H8 concentration in the feed improved permeation properties of all components. A mathematical model was also developed based on Fick's law of diffusion to predict permeation behavior of ternary gas mixtures. The developed model is able to predict the permeability, solubility, diffusivity and activation energy of all components as well as the permeate composition using feed stream data. It was realized that, there is a reasonable agreement between predicted results and experimental data with correlation coefficient (R) of higher than 0.95 and mean squared relative error (MSRE) of lower than 0.2. (C) 2009 Elsevier B.V. All rights reserved.