A prospective panendoscopic evaluation comprising direct laryngoscopy, bronchoscopy, and esophagoscopy was conducted in 100 consecutively seen patients with untreated head and neck primary tumors. Of the patients, 16% (18% counting two third primary lesions found in the 16 patients) had synchronous primary malignant tumors of the aerodigestive tract. Eleven of the 16 patients had silent lesions found only by endoscopy, and 6 (6% of the total group) had lesions found only because the full panendoscopic protocol was followed. Those 6 tumors would not have been discovered as early by clinical examination or by symptom-only directed studies. The initial treatment plan in 7 patients was changed by the panenodscopic findings, This study verifies the high incidence of synchronous primary tumors in the head and neck areas that have been reported in retrospective studies, and suggests that an intensive, full panendoscopic work-up as a screening test in all patients with primary head and neck tumors can be conducted without increased morbidity and yields enough information to justify its cost.