The oxidative degradation of poly(methyl methacrylate) (PMMA) was investigated in chlorobenzene at 50-100°C for various peroxide and polymer concentrations. Unlike thermal degradation, the chain scission of PMMA occurs randomly across the polymer backbone. The samples were analyzed by gel permeation chromatography (GPC) to obtain the time evolution of molecular weight distributions (MWDs). A continuous distribution model for polymer degradation and simultaneous peroxide deactivation was developed assuming that the rate coefficients depend linearly on MW. This model was used to determine the rate coefficients for the oxidative degradation of PMMA. The activation energy, determined from the temperature dependence of the rate coefficients, was 48.2 kcal/mol. © 2001 Elsevier Science Ltd.