We report on the controlled-radical polymerization of the photocleavable o-nitrobenzyl methacrylate (NBMA) and o-nitrobenzyl acrylate (NBA) monomers. Atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), and nitroxide-mediated. polymerization (NMP) have been evaluated. For all methods used, the acrylate-type monomer does not polymerize, or polymerizes very slowly in a noncontrolled manner. The methacrylate-type monomer can be polymerized by RAFT with some degree of control (PDI similar to 1.5) but leading to molar masses up to 11,000 g/mol only. ATRP proved to be the best method since a controlled-polymerization was achieved when conversions are limited to 30%. In this case, polymers with molar masses up to 17,000 g/mol and polydispersity index as low as 1.13 have been obtained. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6504-6513, 2009