A novel catalyst system FeCl2 center dot 4H(2)O/hexamethylphosphoric triamide (HMPA) induced ATRP of MMA in combination with ethyl 2-bromoisobutyrate (EBiB) to give the polymers with controlled molecular weights and narrow molecular weight distributions (MWDs) (Mw/ Mn) < 1.20. With the use of benzyl chloride as the initiator, the MWDs were broader. The ratio of FeCl2 center dot 4H(2)O to HMPA has an effect on the catalytic activity. The reason was discussed based on the result obtained by the isolated crystal of FeCl2 (HMPA)(2) as the catalyst. (C) 2006 Elsevier B.V. All rights reserved.