Based on the process of polymerization, an interpenetrating cell model was proposed for poly(methyl methacrylate) (PMMA). This model was used to account for the presence of dimples on the fracture surface of PMMA when voids are present. PMMA was treated by various methods including mixtures of methanol and chlorophyll, gamma irradiation, at different crosshead speeds and after warm drawing. Micrographs taken of the resulting fracture surface morphologies supported the proposed model.