Adult T cell leukemia (ATL) is one of malignant tumors originated from T-cell system, first described by Takatsuki in 1976. Most cases of ATL have been diagnosed in department of internal medicine and dermatology, because they usually show lymphoadenopathy and skin rash. However, it is rare that ATL has symptoms of otolaryngology. We experienced a case of hoarseness with smoldering ATL. Patient was 51 years old male. He had a tumor in left vocal cord. Pathologically the tumor was malignant lymphoma originated from T cell. HTLV-1 was provided in his serum and proviral DNA was found in ATL cells. First cisplatin was given generally and soon radiotherapy was applied. Reaction of therapy was good and tumor of larynx disappeared gradually. Patient has been alive 6 years from the onset.