The polymerization of methacrylamide (MAM) was performed in aqueous media via reversible addition fragmentation chain transfer (RAFT) polymerization with the dithiobenzoate chain-transfer agent (CTA) 4-cyanopentanoic acid dithiobenzoate (CTP) and 4,4'-azobis(4-cyanopentanoic acid) (V-501) as initiator. The polymerization in unbuffered water at 70 degrees C with a CTP/V-501 ratio of 1.5 was controlled for the first 3 h, after which the molecular weight distribution broadened and a substantial deviation of the experimental from the theoretical molecular weight occurred, presumably because of a loss of CTA functionality at longer polymerization times. Conducting the polymerization in an acidic buffer afforded a well-defined homopolymer (M-n = 23,800 g/mol, M-w/M-n = 1.08). To demonstrate the controlled/living nature of the system, a block copolymer of MAM and acrylamide was successfully prepared (M-n = 33,800 g/mol, M-w/M-n = 1.25) from a polymethacrylamide macro-CTA. (c) 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3141-3152, 2005.