Dermal vascular skin necrosis is associated with a complex group of clinical disorders. Many of these disorders are associated with an underlying abnormality of the PC anticoagulant system or DIC, or both. The clinical appearance and histopathologic features of dermal vascular skin necrosis are similar regardless of the etiology. Acute infectious purpura fulminans is distinct in that an acute vasculitis may be present in addition to microvascular thrombosis. Skin biopsy is a valuable diagnostic tool in the early recognition of these clinical disorders, since skin involvement is frequently an early manifestation of the disease process. Prompt recognition and institution of appropriate therapy at the reversible stages of dermal vascular thrombosis will, it is hoped, reduce the morbidity and mortality currently associated with skin necrosis and purpura fulminans.