Phase diagrams developed for methyl methacrylate containing microemulsions show that the effect of 0.01 M persulfate on the size of the phase stability region is negligible. At higher concentrations (0.1 M) the persulfate showed an influence to be expected from an electrolyte; reduced water solubilization at low surfactant/alcohol ratios and increased solubilization at the highest ratios. Molecular weight dependencies on initiator concentration for both water and organic soluble initiators are shown to follow solution behavior. Added chain transfer agents follow the Mayo equation, however the chain transfer constant for n-C10SH is about 10 times lower than expected, possibly due to incorporation of the thiol group within the micellar interior. Solvent chain transfer alone, being 10 times lower for MMA than for MA, does not give sufficient lowering of molecular weight to give useful comparisons by GPC technique. Comparisons of structure based kinetic differences between emulsions and microemulsions explain solution type behavior observed for microemulsions. © 1980, Taylor & Francis Group, LLC. All rights reserved.