For advanced head and neck cancers that originate in midline structures, bilateral neck dissection should be considered even if the lymph nodes were negative clinically. But, many complications and mortalities may occur in synchronous bilateral neck dissection at sacrifing of both internal jugular vein. Therefore several types of bilateral neck dissection have been proposed, but the effective and safe methods were not determined yet. So, we have prefered the method of synchronous bilateral neck dissection with preserving one internal jugular vein at least. We operated 21 patients who might be expected high incidences of bilateral neck metastases with above type of neck dissection. We analyzed the data of 21 cases(42 sides) retrospectively. The results were as follows: 1) The primary sites were transglottic(33%), supraglottic(29%), hypopharynx(29%) and tongue base(9%). 2) Types of neck dissection were RND(4 sides), MND(7 sides), FND(16 sides), and SND (15 sides). 3) Postoperative complications were minimal and did not influenced morbidity. 4) Mean interval time of neck recurrence was 21 months. Overall neck recurrent rate after bilateral neck dissecton was 19%. In 19%, neck recurrence from positive lymph nodes was 63% and from negative lymph nodes was 37%. As a results, synchronous bilateral neck dissection with preservation of one internal jugular vein minimally should be done in cases which were suspected high incidence of bilateral lymph node metastases for cure and prevention of neck recurrence.