Abstract: A control valve assembly for use in a one-pipe steam heating system in which the passage of steam to each radiator in the system and the return of condensate from each radiator is controlled by individual valve assemblies at each radiator, the valve assemblies being temperature responsive for the regulation of heat provided at each radiator location. Each valve assembly includes a temperature-responsive valve arrangement for controlling the admission of steam to the radiator through a supply pipe and a pressure-responsive valve arrangement for enabling the return of condensate through the same pipe, the entire assembly being compatible with existing fittings for the ready replacement of conventional radiator valves.