Abstract: The process for the production of closed-cell, extra soft polyvinylchloride foam plastics having improved volume stability at elevated temperatures. The process includes heating a plastisol or plastigel comprised of a plasticizer and foaming agent containing polyvinyl chloride or vinyl chloride copolymerizate in a pressure mold at a pressure of up to 300 atm. to a temperature of 150.degree. to 180.degree. C. for 1 to 2 hours. The plastigel or plastisol is cooled, at an unchanged closing force of the press of said pressure mold, to a temperature of 20.degree. to 70.degree. C. The plastigel or plastisol is removed from the pressure mold, a crude foam plastic forming. The crude foam plastic is heated under a gas pressure of 2 to 10 atm. to a temperature of 140.degree. to 170.degree. C. The crude foam plastic is cooled at said pressure of 2 to 10 atm. to a temperature of 100.degree. to 130.degree. C. The pressure is lowered to atmospheric pressure, the foam plastic simultaneous expanding.