Measurements have been made of the oxidation products of methyl formate and methyl acetate as a function of temperature (253-324 K). Both processes show the occurrence of the alpha-ester rearrangement channel RC(O)OCH2O. --> RC(O)OH + HCO, which has an activation energy of similar to10 kcal mol(-1). Reaction of hydroxyl radicals with methyl formate occurs with roughly equal efficiency at both of the carbon atoms, while OH-reaction with methyl acetate leads to 30-40% attack at the acetate group.