A kinetic model has been proposed for a free-radical polymerization in the presence of an added initiator and an addition-fragmentation agent. The present one is considered as a special case where the addition-fragmentation agent acts also as an initiator. The model takes into account the chain termination process by way of primary radicals and excludes the mutual termination of primary radicals. The general model has been applied to the case of methyl methacrylate (MMA) polymerization in the presence of a peroxyketal, viz., ethyl 2-[((1-n-butoxyethyl)peroxy)ethyl]propenoate (EBEPEP) as the addition-fragmentation agent. An expression for the molar mass of the formed polymer has also been derived considering the various initiation and termination processes as an improvement over the conventional Mayo equation. The kinetics were performed at various temperatures to prove the validity of the equation, and the different kinetics factors relevant to initiation, addition-fragmentation, and primary radical termination were evaluated. The addition-fragmentation agent in this case manifested retardation until 70 degrees C beyond which the polymerization rate increased with increase in concentration of addition-fragmentation agent caused by the thermal decomposition of the peroxy group on EBEPEP.