We reviewed the histopathologic findings in 28 specimens from 25 patients who had skin lesions associated with lupus anticoagulant. The clinical lesions were ulcers, gangrene, thrombophlebitis, hemorrhage, and cutaneous necrosis. Noninflammatory thrombosis of small dermal vessels was observed in all 8 biopsy specimens from gangrene lesions, 10 of 13 specimens from ulcer lesions, and 2 of 5 specimens from thrombophlebitis lesions. Necrotizing vasculitis was not significant in these biopsy specimens. Immunofluorescence findings included a positive lupus band test in lupus erythematosus-associated disease and nonspecific deposits in occasional cases. Focal noninflammatory intravascular coagulation is responsible for the microscopic and clinical skin lesions in these patients.