Abstract: Incorporating 500 to 5,000, preferably 2,000 to 4,000 parts per million of Fischer-Tropsch wax of high congealing point into beads of expandable polystyrene made by suspension polymerization yields greater advantages, and conditions (time, temperatures, and recipe) of the polymerization become less critical. The drying or conditioning step before the pre-expansion under particular conditions to generate a suitable cell structure need not be followed, and a step of coating with zinc stearate or the like before the pre-expansion may be omitted. Unexpanded beads are obtained which yield consistent cell structure, independent of conditions of their storage. Beads of higher pentane content can be used, and final articles of lower density may be obtained. The throughput of the pre-expander may be increased, and the beads, after pre-expansion, have good free-flowing (reduced clumping) and mold-filling characteristics.