Small cell lung cancer was diagnosed in a 54-year-old man in 1997. He had received 5 cycles of systemic chemotherapy and thoracic irradiation since 1997, and a favorable response had been achieved. In August 2001, pro-GRP was again elevated, and he was readmitted. Bronchoscopic findings revealed a white dendritic endobronchial mass on a cheese-like plug obstructing the left upper bronchus division. Numerous mucor hyphe and cancer cells were detected by transbronchial biopsy, and a fungal culture disclosed mucor. Although no antifungal drug was administered, the bronchial lesion disappeared after removal with biopsy forceps and 2 cycles of systemic anticancer chemotherapy. Endobronchial involvement of mucormycosis is rare and this case is unique because of the peculiar bronchoscopic finding with the endobronchial lesion.