Objective: To assess the role of positron emission tomography (PET) in the management of unknown primary carcinoma of the head and neck region. Design and Setting: Prospective case series at an academic medical center. Patients: Twenty-six patients with an open excisional biopsyorafine-needleaspirationbiopsyfindingthatconfirmed squamous cell carcinoma of the cervical lymph nodes and no visible primary tumor (as determined by results of a comprehensive physical examination and computed tomography and/or magnetic resonance imaging) underwent PET. The standard evaluation consisted of a comprehensive head andneckexaminationthatincludedfiberopticlaryngoscopy/ nasopharyngoscopy, computed tomography and/or magnetic resonance imaging, and PET followed by panendoscopy with selected biopsies and tonsillectomy. Main Outcome Measures: Sensitivity, specificity, and positive and negative predictive values of PET to detect an occult primary tumor. (REPRINTED) ARCH OTOLARYNGOL HEAD NECK SURG/ VOL 131, JULY 2005 WWW.ARCHOTO.COM 626