A case of simultaneous occurence of two adenoid cystic carcinoma in bilateral parotid glands was reported. The patient was a sixty-five-year-old male complaining of foreign body sensa tion of his neck. In the left parotid gland, there were two tumors : one in the superficial lobe, the other in the deep lobe. Two tumors were also found in the right parotid gland : both in the superficial lobe. Initial histopathological diagnosis of these tumors was pleomorphic adenoma, which was finally corrected as adenoid cystic carcinoma. Several factors for the induction of multiple adenoid cystic carcinomas in parotid gland were discussed. This is the first report of multiple occurence of adenoid cystic carcinoma in bilateral parotid glands.