A small proportion of patients with head and neck cancer have a malignancy that has metastasized to a lymph node in the neck from an unknown “primary site” in the mouth or throat. Following a search for the origin of the cancer (primary site) with a physical exam and CT scan, biopsy of suspected primary sites are obtained under anesthesia. The primary cancer site can be found in about 40% of patients. Treatment ususally consists of radiation either alone, or combined with an operation to remove the malignant lymph nodes in the neck. Detection of the primary site will influence the areas included in the radiation fields and the “fractionation schedule,” (whether the treatment is given once or twice a day). Even if the primary site is not found, the chance of cure is relatively high.