The effect of pressure on gas permeability of a rubbery polymer, 1,2-polybutadiene, is investigated for 15 gases with various molecular sizes and solubilities in the ranges of pressure up to 110 atm at 25 degrees C. The permeability for slightly soluble gases (He, Ne, H-2, N-2, O-2, and Ar) decreases with increasing pressure, and that for soluble gases (CH4, Kr, CO2, N2O, C2H4, Xe, C2H6, C3H6, and C3H8) increases with increasing pressure. Logarithms of permeability coefficient versus feed-gas pressure for the slightly soluble gases, CHI and Kr, is linear within each pressure range, whereas such plots become convex toward the pressure axis for more soluble gases, such as CO2, N2O, C2H4, Xe, C2H6, C3H6, and C3H8. By analyzing the pressure dependence of permeability using sorption data of the gases, contributions of concentration and hydrostatic pressure to the gas diffusivity are estimated.