A 67-year-old man who had worked as an aluminum grinder had been given a diagnosis of pneumoconiosis. Ten years later, he was admitted with fever, dyspnea on exertion, and numbness. Chest roentgenograms showed linear-reticular shadows in both lower lung fields. ELISA-based tests were positive for perinuclear anti-neutrophil cytoplasmic antibody (P-ANCA). Renal biopsy specimens disclosed crescentic glomerulonephritis and angiitis of small arteries. Our diagnosis was microscopic polyangiitis accompanying interstitial pneumonia with aluminum lung. The results of high-energy dispersion X-ray microanalysis indicated that the patient's lungs contained aluminum. His general condition improved with the administration of corticosteroid and immunosuppressive agents, and his chief symptoms disappeared.