Records of nine patients (aged ten to sixty-four years) seen at the Mayo Clinic with the typical cutaneous lesions of Degos' syndrome were reviewed. The three patients who died all had central nervous system involvement. The six patients now alive have been evaluated for two to fourteen years and have had their disease for four to fourteen years. Histopathologic examination was performed in all nine cases (total of 27 skin biopsy specimens). Wedge-shaped infarction in the dermis and subcutaneous tissue was observed only in one biopsy specimen from each of three patients, and the infarction occurred in older, well-formed skin lesions. Thrombosis of the arterioles was found in two patients. Hyperkeratosis and dermal acid mucopolysaccharide deposits were common. The most consistent histopathologic finding was lymphocytic infiltrate around and in the walls of venules and arterioles. Various degrees of lymphocyte-mediated necrotizing vasculitis were present in all patients.