Adenocarcinoma ex pleomorphic adenoma is a rare tumor, and thus the management of the tumor has not been established.The retrospective review of the clinical records at Okayama University was performed.We present five cases of adenocarcinoma ex pleomorphic adenoma of the head and neck, including a rare case with nasopharyngeal adenocarcinoma ex pleomorphic adenoma. There was no response to chemotherapy with nedaplatin and 5-FU, but the nasopharyngeal adenocarcinoma ex pleomorphic adenoma showed a remarkable regression after the administration of docetaxel.The combination therapy that includes docetaxel may be a promising treatment for adenocarcinoma ex pleomorphic adenoma of the head and neck.