Suspension polymerization of styrene was performed using calcium tertiary phosphate as the suspension stabilizer and sodium dodecylbenzenesulfonate as the suspension co-stabilizer. It was investigated how the stepwise and continuous reduction in impeller speed over the course of polymerization affected the final particle size distribution. Transient mean droplet diameters, final particle size distributions and final mean particle sizes were significantly affected by the degree of impeller speed reduction and the polymerization conversion. Three step reduction in the range of conversion from 0 to 0.45 was found to produce polymer particles of the most uniform size.