An autopsy case of primary pulmonary choriocarcinoma that manifested as diffuse alveolar hemorrhage is reported. A 44-year-old nurse presented with fever, dry cough, hemoptysis, and progressive dyspnea, and died after a downhill course of 2 weeks. Chest radiographs showed diffuse parenchymal shadows throughout the entire lung and a nodular lesion in the right lower lobe. Findings suggestive of acute renal failure were not seen. The autopsy revealed primary pure choriocarcinoma of the right lower lobe and diffuse alveolar hemorrhage throughout the entire lung. Findings of small vessel vasculitis ("pulmonary alveolar capillaritis") were not observed, and extensive neoplastic involvement of the pulmonary vasculature was considered the cause of the diffuse alveolar hemorrhage. Small metastatic foci were found in the liver, adrenal glands, pancreas, and ovaries. This case shows that primary pulmonary neoplasms, on rare occasions, can produce the clinical and pathologic features of diffuse alveolar hemorrhage, probably through elevated pulmonary venous pressure caused by extensive destruction of the vasculature.