Poly(ethylene terephthalate) PET and poly(methyl methacrylate) PMMA blends were made by melt mixing in a batch reactor. Three different weight ratios of PET : PMMA (25:75, 50:50 and 75:25) were chosen to study the effect of blend composition on the degradation kinetics. A relationship between the fractional volatiles evolved per unit time and the fraction of polymer degraded is established. The kinetic parameters for degradation were found using modified Avrami's non-isothermal equation. Parameters like degradation rate constant (k) and order of degradation (n), were evaluated for the virgin polymers and the blends.