Background and objectives : There may be frequent lymphatic neck metastasis among supraglottic cancer patients after their primary surgery. The aim of this study was to evaluate the effectiveness of prophylactic neck dissections in supraglottic cancer patients to lower the neck metastasis. Material and method : The authors retrospectively reviewed medical records of 52 patients (7 females. 45 males) who had received the operations for the supraglottic cancer from 1995 to 2000. They were preoperatively examined with Computer Tomographic images, and also examined by the cervical neck palpations. Postoperative pathologic specimens were reviewed and the Pathologic stagings were confirmed by the pathologist. Results : Among 52 patients who received surgery for supraglottic carcinoma, 5 patients received ipsilateral neck dissection, 12 patients received ipsilateral neck dissection with postoperative radiation therapy, 10 Patients received bilateral neck dissection and 25 patients received bilateral neck dissection with postoperative radiation treatment. In comparison of the data of N0 to N+ conversion rate of neck, there were 11 ipsilateral T3 N0 patients and 2 patients(18%) were converted to N+ status, and there were 8 Patients with T4 N0 stages, and 3 patients(38%) were converted to N+ status. In comparing the data of contralateral neck dissection on N0 patient, there were 8 patients of T3 N0 patients, and there was 1 patient (13%) who showed recurrence. There were 5 patients of T4 N0 stages and there was 1(20%) patient with recurrences. When the ipsilateral N stages were N2a, and N2b, there 1 case of contraleral N+ conversions, respectively. In recurrences, there were 2 patients of N2b staged patients and 1 patient of N2c patient that showed recurrence during the follow up period. Conclusion : This data shows that at least an ipsilateral neck dissection is necessary in order to prevent the recurrences, and also suggests that bilateral neck dissection is necessary for the higher T stage. Since the higher N staged patients showed higher rate of recurrence, so that neck dissection is mandatory for the higher N staged patients.