The degree of polymerization was investigated in the homo-polymerization of ethyl and methyl acrylate in solution at 50°C. Molecular weights were determined by osmometry and viscometry. The mechanism of chain termination was found to be the combination of growing radicals in the polymerization of both monomers. The equation describing the degree of polymerization was derived considering the reactions of vibrationally excited radicals. Theoretical curves were found to be in good agreement with experimental data. Chain transfer constants were determined accordingly; in the EA/AIBN/DMF/50°C system CM= 9.0 × 1CT−5, Cs= 1.0 ×lo−5, Cs* = 8.3 × 10−5, and in the MA/AIBN/DMF/50°C system C. = 8.0 × 10−5, Cs= 3.4 ×10−5, Cs* = 12.5 × 10−5