To determine the optimal type of neck dissection for N0 cases of squamous cell carcinoma of the tongue, the pattern of occult metastases was evaluated.<BR>Between 1974 and 1997, 35 N0 cases without local recurrence were histologically confirmed to have cervical lymph node metastasis. Of the 35 patients, 4 underwent elective neck dissection (END) and the others underwent therapeutic neck dissection (TND). Recurrence in the dissected area developed in 6 patients who had received TND. In the END group, the number of positive nodes was 1 or 2, and neck involvement was located at levels I to III. In the TND group, the number of positive nodes was 1 or 2 in 28 patients and 3 or more in 3 patients. Level I to III nodes were involved in 26 patients, level IV in 2, and level V in 3.<BR>Supraomohyoid neck dissection can be considered a standard elective treatment for squamous cell carcinoma of the tongue. However, in patients who subsequently developed cervical metastasis, either radical neck dissection or modified radical neck dissection should be performed.