The polymn. of Me methacrylate (I) [80-62-6] in DMF with aged Cr(OAc)2 (II) [628-52-4] and Bz2O2 (III) [94-36-0], previously formulated as a living radical polymn., was investigated. The reaction between II and III gives besides N-methylformamidomethyl benzoate the N-methylformamidomethylchromium(III) cation as an intermediate, which itself may react with III to form addnl. free radicals at a rate faster than that of III thermolysis. Thus, the polymn. of I in this system could be a normal radical one with free and uncomplexed radicals. The increase of the d.p. with aging and monomer conversion is explained by the decreasing rate of the radical forming reactions and the onset of the gel effect.