The polymerization of vinyl acetate in one-phase o/w microemulsions stabilized with Aerosol OT (AOT) is examined as a function of concentration and type of initiator(V-50 and KPS) and temperature. Conversions and reaction rates increase with increasing concentration of V-50 and temperature. Faster polymerization rates and higher conversions are achieved with RPS because of the different electrostatic interactions between the charged microemulsion droplets and the free radicals of KPS and V-50. Average molar masses and polydispersity indexes ((M) over bar(W)/(M) over bar(n)) are much smaller than those observed in emulsion polymerization using the same surfactant, even at high conversions. Analysis of the molar mass distribution indicates that chain-transfer reactions to monomer are the controlling chain-growth mechanism in the polymerization of vinyl acetate in AOT microemulsions at all conversions.