The polymerization kinetics of C4, C8, and C12n-alkyl acrylates are characterized by monomer orders of 1.5 or greater and in the case of the C8and C12esters an initiator exponent of less than 0.5. Various explanations for the high monomer exponent have been considered including mechanisms based on intramolecular degradative transfer or the presence of a dimeric monomer species. Initiator exponents of less than 0.5 are explained in terms of a chain length dependence of the diffusion-controlled termination constant. Rotating sector curves have been obtained for the acrylates, and this data for n-butyl acrylate yields a value of 1.4×106dm3/ (mole)(sec) for the termination constant.