Poly(methyl methacrylate) (PMMA) was gamma-irradiated (5-20 kGy) by a Cs-137 source at room temperature in air. The changes in the molecular structure attributed to gamma-irradiation were studied by mechanical testing (flexure and hardness), size-exclusion chromatography, differential scanning calorimetry, thermal gravimetric analysis, and both Fourier transform infrared and solution C-13-NMR spectroscopy. Scanning electron microscopy was used to investigate the influence of the dose of gamma rays on the fracture behavior of PMMA. The experimental results confirm that the PMMA degradation process involves chain scission. It was also observed that PMMA presents a brittle fracture mechanism and modifications in the color, becoming yellowish. The mechanical property curves show a similar pattern when the gamma-radiation dose increases.