Forty cases of overlap syndrome of progressive systemic sclerosis and polymyositis (OS PSS-PM) are reported in this paper. All of these cases had manifestations of both PSS and PM as well as Raynaud's phenomenon. The sclerodermatous skin changes were diffused over the whole body in most cases. All cases had muscular weakness, elevated skeletal muscle enzyme levels and muscle damage as seen on the electromyogram. Histopathologic changes showed characteristics of myositis. There was noticeable systemic involvement, especially with the digestive and circulatory systems. Serologic examination frequently revealed autoantibodies. The patients responded well to traditional Chinese medicines and corticosteroids.