Abstract: Seamless hollow-bodied objects of expanded polystyrene are made by a method in which polystyrene material in bead form is agglomerated about a solid removable core in a split mold. The mold halves are opened and the solid core is removed, leaving at least two preliminary sections in contact with the mold halves. The mold is reclosed, and an inflatable core is inserted and inflated to desired dimensions. The inflatable core is supplied with steam for its inflation and the polystyrene heating is completed. After deflation and removal of the inflatable core and opening of the mold halves, there is obtained a desired seamless hollow article having smooth surfaces inside and out.