A 51-year-old male with undifferentiated adenocarcinoma of the lung associated with sarcoidosis is reported. Scalenus node biopsy and open thoracotomy revealed sarcoid granuloma. High levels of serum angiotensin-converting enzyme and ocular findings also suggested sarcoidosis. No malignant cells were recognized by repeat lymph node biopsy. However, post-mortem examination showed bronchial carcinoma; no sarcoid granuloma was found. The diagnostically difficult points of our case are discussed.