A 34-year-old male patient was admitted to our hospital because of progressive exertional dyspnea and weight loss (8 kg in one year). Twelve years previously, he had had an episode of uveitis accompanied with bilateral hilar lymphadenopathy. Scalene node biopsy at that time revealed non-caseating epithelioid granulomas. Four years later, a follow-up chest radiograph showed bilateral fine nodular lesions. The bilateral parenchymal lesions gradually increased in density, and eventually, formed a confluent air-space consolidation containing multi-ocular cavities. On physical examination, the patient was emaciated (Ht 165 cm, Wt 40 kg). Nodular cutaneous lesions were present on his face and elbows. Hypoxemia with hypercapnea (PaO2 56 Torr, PaCO2 51 Torr) was noted. Repeated sputum cultures yielded negative results for acid-fast bacilli, fungi, and other pathological organisms. A transbronchial lung biopsy specimen obtained from near the cavitary lesion revealed non-caseating granulomas compatible with sarcoidosis. Skin lesion biopsy showed similar findings. The cavitation, was therefore considered to be due to ischemic necrosis of confluent sarcoid granulomas. Prednisolone (40 mg daily) was given with a prompt improvement of symptoms including dyspnea, as well as the radiographic abnormalities. We conclude that uncomplicated pulmonary sarcoidosis may rarely develop into an aggressive parenchymal disease with cavitation. It is of importance to differentiate such cases from infectious diseases (tuberculosis, mycosis etc.) because of the need for corticosteroid treatment.