Diffuse systemic sclerosis (SSc) is a chronic disease of unknown cause characterized by diffuse fibrosis and vascular abnormalities in the skin and internal organs. Pathogenesis of SSc involves immunologic mechanisms, vascular damage and activation of fibroblasts. SSc varies in severity and progression; most patients eventually develop visceral complications, which are the usual causes of death. No drug significantly influences the natural history of SSc overall, but various drugs are of value in treating specific symptoms or organ systems. This review discusses pathogenesis, clinical manifestations and possible treatment of SSc.