Homogeneous atom transfer radical polymerization of methyl methacrylate (MMA) under microwave irradiation (MI) with low concentration of initiating system [ethyl 2-bromobutyrate (EBB)/CuCl/N,N,N',N'',N"-pentamethyldiethylenetriamine (PMDETA)] was successfully carried out in N,N-dimethylformamide (DMF) at 69 degreesC. Plots of In ([M](0)/[M]) vs. time and molecular weight evolution vs. conversion showed a linear dependence. A 27.3% conversion for a polymer with number-average molecular weight (M.) of 57,280 and a polydispersity index (PDI) of 1.19, was obtained under MI (360 W) with the ratio of [MMA](0)/[EBB](0)/[CuCl](0)/[PMDETA](0) = 2400/1/2/2 in only 150 min; but 963 min was needed under conventional heating (CH) process to reach a 26.0% conversion (M. = 63,990 and PDI = 1.14) under identical polymerization conditions, indicating a significant enhancement of the polymerization rate under MI. (C) 2003 Elsevier Science Ltd. All rights reserved.