Models based on a mass-diffusion theory successfully represent the growth and collapse of gas bubbles in an epoxy resin. A quantitative evaluation of the steady-state diffusion equations requires values for the diffusion coefficient and the solubility of the mobile species within the resin precursor. These parameters are affected by changes in temperature and/or pressure, and they are generally not measured as part of a processing schedule. Models have been evaluated that predict the temperature dependence of the gas diffusion coefficient in the resin. A free volume approach describes the viscosity of the resin successfully at temperatures of up to 100 K above the glass-transition temperature. At higher temperatures, a thermal-energy-barrier approach is more appropriate. A direct correlation between the viscosity of the resin and the gas diffusion coefficient is proposed which is considered to be applicable to any gas/resin system where specific component interactions are negligible and the solute concentration is sufficiently low that it does not affect the free volume of the medium.