Systemic lupus erythematosus (SLE) is a well-known acute and/or chronic multisystem disease of complex autoimmune nature, having predilection for cardiovascular system. While its cardiac manifestations have been adequately studied, there is paucity of information on its vascular manifestations. Accordingly, we studied the incidence of vascular manifestations in 50 consecutive SLE patients seen at our institutions and in private practice during the past 12 years. Systemic hypertension (44%) was the most common vascular manifestation followed by vasculitis (30%), Raynaud's phenomenon (26%), telangiectasis (20%), premature coronary atherosclerosis (6%), digital ulceration (6%), thrombophlebitis (6%), pulmonary hypertension (4%) and portal hypertension (4%). Diffuse systemic vasculitis similar to polyarteritis nodosa was rare (2%). Often more than one lesion was found in the same patient. The clinical diagnosis of these vascular manifestations in the context of the primary disease (SLE) usually does not pose any difficulty except when they antedate it. We also studied the pathology and pathogenesis of some of these vascular lesions in both autopsy and biopsy specimens by both light microscopy and immunofluorescent techniques. Our results as well as those of others who also studied these lesions indicate that immune complex deposition and subsequent complement activation play an important role in the pathogenesis of vasculitis, coronary arteritis and premature coronary atherosclerosis. Corticosteroids and vasodilators remain the drugs of choice for the management of the majority of the symptoms arising from the vascular lesions of SLE.