External auditory canal (EAC) carcinoma is a comparatively rare disease. We herein report a case of adenoid cystic carcinoma of the EAC. In March 2004, a 67-year-old woman was referred to our department because of swelling and pain in her left ear. We suspected an EAC tumor, and a biopsy of the lesion was performed. The presence of an adenoid cystic carcinoma was confirmed, and the patient underwent an excision of the EAC and postoperative irradiation. No evidence of recurrence was seen at a Five-year follow-up examination. Adenoid cystic carcinoma of the EAC is a rare disease. Most patients only complain of ear pain. This symptom is similar to that of otitis externa. The lack of specific clinical signs makes a diagnosis of adenoid cystic carcinoma of the EAC difficult. Early recognition by biopsy is essential because the management and prognosis of this disease are determined by the extent of the tumor. We suggest that if an EAC tumor is suspected, a biopsy should be immediately performed for the early diagnosis and treatment of this condition.