An experimental investigation and a detailed kinetic model of the bulk free radical polymerization of styrene initiated by diperoxyester initiators are presented. The experiments were conducted through the full conversion range at various temperatures and initiator concentrations. It is shown that the employing of such initiators leads to the formation of polymers having substantially higher molecular weight and narrower molecular weight distribution than those obtained by the conventional monofunctional initiators. The current investigation has also found that high monomer conversion and high molecular weight can be obtained simultaneously within a reduced reaction time period. Model predictions were compared with experimental data and were found to be in agreement.