Miscible polymer blends based on various ratios of poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) PMMA) were prepared in film form by the solution casting technique using benzene as a common solvent. The thermal decomposition behavior of these blends and their individual homopolymers before and after gamma-irradiation at various doses (50-250 kGy) was investigated. The thermogravimetric analysis technique was utilized to determine the temperatures at which the maximum value of the rate of reaction (T-max) occurs and the kinetic parameters of the thermal decomposition. The rate of reaction curves of the individual homopolymers or their blends before or after gamma-irradiation displayed similar trends in which the T-max corresponding to all polymers was found to exist in the same position but with different values. These findings and the visual observations of the blend solutions and the transparency of the films gave support to the complete miscibility of these blends. Three transitions were observed along the reaction rate versus temperature curves; the first was around 100-200 degrees C with no defined T-max which may arise from the evaporation of the solvent. The second T-max was in the 340-380 degrees C range, which depended on the polymer blend and the gamma-irradiation condition. A third transition was seen in the rate of reaction curves only for pure PVAc and its blends with PMMA with ratios up to 50%, regardless of gamma-irradiation. We concluded that gamma-irradiation improved the thermal stability of PVAc/PMMA blends, even though the PMMA polymer was degradable by gamma irradiation. (c) 2005 Wiley Periodicals, Inc.