The properties of organic liquids affecting the environmental stress crazing in glassy poly(methyl methacrylate), polycarbonate and polyvinyl chloride were examined with reference to the diffusivity into the polymers. The isochronal bending tests for the sheet specimens were conducted by a traditional method using the elliptical bending device in environments of five alcohols, four n-alkanes and three good solvents at 30degreesC. The diffusivity of these liquids exclusive of n-pentane and the solvents was evaluated by measuring the weight gain of specimen under the accelerated soaking at 52degreesC. The absorption rate of each liquid, given by an initial weight gain per unit time, was shown to be correlated with a new factor consisting of the viscosity and molar volume of environmental liquid and of a ratio of dielectric constant of liquid to that of polymer. The critical crazing strains in alcohols and n-alkanes were also demonstrated to relate to this factor. In good solvents no crazing but dissolution of polymer surface was observed. It thus may be concluded that the crazing is strongly correlated with the diffusivity of environmental liquid, and in addition that the liquid with the above factor of greater value clearly tends to cause the environmental crazing in glassy polymers.