The values of k2p/kt for methyl acrylate polymerization initiated by benzöyl peroxide and azo-bis izobutyronitrile have been determined. By using Matheson’s values for kpand kt, k2p /kt has been calculated. From these results, it is seen that the eguation of rate of termination must be given without the factor 2 which is used by some poly- mer chemists.