Predissolving polystyrene into the styrene monomer prior to homogenization in miniemulsions created using cetyl alcohol as the cosurfactant has been shown to result in a large increase in the polymerization rate and reduction in the particle size compared to similar systems with no predissolved polymer. This phenomenon has been termed "enhanced droplet nucleation". The effects of varying the molecular weight and end group of the predissolved polystyrene in sodium lauryl sulfate/cetyl alcohol stabilized styrene miniemulsions are investigated here to gain a clearer understanding of this phenomenon. Predissolving polystyrene with either H or SO3- end groups and molecular weights over a range from M-n = 39 000 to 206 000 g/mol results in the same level of enhancement in the kinetics independent of the polymer characteristics. This is taken as evidence against either droplet surface modification or a change in droplet viscosity being the determining factor in"enhanced droplet nucleation". However, measurement of the droplet size when no polymer is included indicates that these droplets undergo degradation by which the average size increases over time. Therefore, it is suggested the predominant; cause of "enhanced droplet nucleation" from the addition of polymer is that the polymer adds extra stability to the miniemulsion droplets both pries to and during the polymerization. This is supported by calorimetric and particle size data.