An autopsy case of SLE died from acute and diffuse pulmonary hemorrhage is presented. A 50 year-old woman with SLE was admitted to our hospital because of high fever, butterfly rash, discoid skin lesions and renal dysfunction. She died from acute respiratory failure before initiation of the therapy with corticosteroid. Autopsy findings revealed a massive acute intrapulmonary hemorrhage. Histological study demonstrated a pulmonary arterial vasculitis with prominent fibrinoid necrosis at muscular pulmonary artery. No remarkable deposit of immunoglobulins and complements was found within the alveolar walls and pulmonary vessels by immunofluorescence and electron microscopy. Renal histology revealed diffuse proliferative glomerulonephritis with fibrinoid necrosis, crescent formation and wireloop lesions compatible with type IVb according to the WHO classification. The granular deposit of IgM, C3 and Clq, and electron dense deposit was found by immunofluorescence and by electron microscopy, respectively, in the kidney. The small arteries and veins in other organs, such as liver, spleen, bladder, ovary and rectum also revealed fibrinoid vasculitis. Acute infectious lesion was not observed in any tissue examined. The diffuse pulmonary hemorrhage in SLE could be one of the manifestations of active and severe systemic vasculitis.