The reactivity parameters of the copolymerization of N,N-bis(2-methacryloyloxyethyl)-p-toluidine (BMAT) (M1) with methyl methacrylate (MMA) (M2) in 1,4-dioxane, i.e. r1 = 1.07 +/- 0.20, and r2 = 0.11 +/- 0.19, and with bisphenol-A bis(2-hydroxypropyl methacrylate) (Bis-GMA) (M2) in benzene, i.e. r1 = 0.58 +/- 0.04, and r2 = 0.03 +/- 0.03, were determined at 60-degrees-C at low concentration and low conversion (approximately 5%) of the monomers. Strongly delayed gelation occurred during the copolymerization of BMAT and MMA at monomer conversions of 20-30%, relatively independently of the composition of the monomer mixture. The efficiency of BMAT and N-acryloyl-N’-phenylpiperazine as activators in the redox initiated copolymerization of Bis-GMA in dental composites at ambient temperatures was found to be comparatively low. In the case where BMAT was used in equimolar proportions to benzoyl peroxide the former component was not detectable in the extract of the cured composite.