Understanding the gas diffusion and evaporation behavior in a polymeric resin under vacuum is of great importance because many types of polymer and composite products are manufactured by applying a vacuum to the production system. This article proposes a theoretical model that can describe bubble growth under vacuum by combining the mechanisms of gas diffusion and evaporation. To confirm such a model, we carried out experimental analyses including evaporation experiments with a bell jar or a tube as well as vacuum-assisted resin transfer molding (VARTM). Particularly in the VARTM process, it was identified that many bubbles were nucleated and grew at the fiber-matrix interface due to the applied vacuum pressure. Those results suggest that more attention should be paid to vacuum-assisted material processing to prevent bubbles from existing in the final products. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers