Helium, deuterium, and neon permeability, diffusivity, and solubility have been measured for CGW‐7740 glass. The results indicate that gas migration occurs primarily through the silica‐rich phase. Reaction of deuterium with the glass structure is evident at temperatures exceeding 300°C. The activation energy associated with this reaction is approximately 15 kcal/mole, which is the same as that for hydroxyl formation in vitreous silica.