Abstract: The object of the present invention is to provide a reinforcement structure for a rear pillar of automobiles. In this structure, a reinforcing panel, forming the upper portion of the rear pillar, is integrated with the welded junction between an inside upper quarter panel and a rear lower roof rail, thus forming a closed cavity within the rear pillar while maximizing the structural strength of rear roof rails. This structure thus allows the top edge of the body's rear portion, formed by the rear roof rails, to effectively and stably support a rear hatch and effectively intercepts noise transmitted from tires of wheels into the passenger compartment through the rear pillars during operation of the automobile. The reinforcing panel extends in a space defined between the inside upper quarter panel and a side panel and is integrated with the lower end of the inside upper quarter panel at its lower end. This reinforcing panel is also integrated with the upper end of the side panel at its upper end portion.