The incidence of occult cervical metastasis in oral cavity cancer, even in early stages, is significant, necessitating elective treatment of the neck in a majority of cases. There is no method of imaging or other examination that will detect microscopic foci of metastatic disease in cervical lymph nodes. Immunohistochemical and molecular analysis of neck specimens reveals the incidence of occult metastases to be higher than revealed by light microscopy with ordinary hematoxylin and eosin staining. The neck may be treated electively by surgery or irradiation. Surgery has the advantage of permitting pathological staging of the neck, avoiding unnecessary radiation treatment and indicating cases where adjuvant therapy should be employed. As oral cavity cancer rarely metastasizes to level V, a radical or modified radical neck dissection of all five node levels is not necessary. Selective dissection of levels I-III ("supraomohyoid neck dissection") is the usual procedure of choice for elective dissection of the neck. Most of the relatively small number of isolated metastasis to level IV are from primary tumours of the tongue, which are known to produce "skip" metastases. Thus an "extended supraomohyoid neck dissection" of levels I-IV is recommended by some authors for elective treatment of the neck in tongue cancer. A number of recent prospective multi-institutional studies have demonstrated that sublevel IIB is rarely involved with isolated metastasis from oral cavity primary tumours, except from some tongue cancers. Thus it is justifiable to omit dissection of sublevel IIB in elective treatment of most cases of oral cavity cancer. Bilateral neck dissection should be performed in elective treatment of tumours involving midline structures, and in patients with ipsilateral neck metastasis.