A detailed study of the factors affecting the dissolution rate of poly(methyl methacrylate) (PMMA) showed that the magnitude of the increase in the dissolution rate of irradiated PMMA could not entirely be attributed to the reduction in MW. The formation of non-polymeric volatile fragments by radiation exposure causes a large increase in solvent flux into the polymer matrix, thereby causing a large increase in dissolution rate of exposed PMMA. The vola tilization of these low MW fragments causes an increase in the excess free volume (microporosity) of the glassy PMMA. The relative magnitudes of the contribution of MW reduction and formation of volatile matter on the increase in solubility rate of the irradiated polymer were found to depend on the molecular size of the solvent and on the enthalpy of mixing. -- AATA