A 65-year-old woman with previously known rheumatoid arthritis and chronic renal failure of possible glomerular origin was admitted to the hospital because of hemoptysis and respiratory insufficiency. Antineutrophil cytoplasmic antibodies (ANCAs) with antimyeloperoxidase activity were detected in her serum. The lung biopsy specimen evidenced alveolar hemorrhage. Under immunosuppressive therapy with steroids and cyclophosphamide, the patient's condition improved both clinically and radiologically, and the ANCA became negative after 6 months' therapy.