Abstract: A process for treating expanded polystyrene which comprises the step of softening a waste material of expanded polystyrene by immersing the material in a petroleum organic solvent mainly comprising liquid hydrocarbons in the neighborhood of the site yielding the waste material to form a dough-form intermediate product, the step of separating the intermediate product from the solvent by physical means, and the step of recovering and reclaiming the polystyrene contained in the intermediate product. The organic solvent is suitable a mixture mainly comprising aromatic hydrocarbons and aliphatic hydrocarbons and having the content of the aromatic hydrocarbons of 20 to less than 60 Wt %. According to this process, a low-tack intermediate product can be produced in a short time with an inexpensive organic solvent, and high quality polystyrene can be reclaimed from the intermediate product.