Since polar reactants can adsorb microwave irradiation, chemists can utilize the microwave oven for some organic reactions. In this paper, we report a rapid conversion of lactams to cyclic imides using peracetic acid (CH(3)-CO(3)H) and manganic chloride (MnCl(2)) in ethyl acetate (CH(3)-COOEt) as a solvent and under microwave irradiation (90 W, 5 min) in good yields.