A prospective CT study of seventeen patients with metastatic cervical adenopathy from tumors at an unknown primary site, believed most likely to be in the upper aerodigestive tract, was performed. All patients had normal endoscopic examinations performed by an otolaryngologist before the CT study. CT suggested a primary site in ten cases, of which four were confirmed by surgery or biopsy. In four cases, CT did not identify a suspicious site and no primary site was identified during triple endoscopy, sometimes with blind biopsies. CT was able to suggest correct causes other than carcinoma in three cases and gave useful information about the extent of nodal disease. CT should be used as part of the routine evaluation of patients with this clinical problem. A diagnostic algorithm is suggested in which CT is integrated with modern endoscopic and aspiration cytologic techniques.