The extent of tumor was staged independently using conventional clinical methods and high-resolution computed tomography (CT) in 100 patients with tumors at the base of the skull, nasopharynx, oropharynx, hypopharynx, larynx, nose, and paranasal sinuses. Conventional clinical methods used for staging included physical examination, routine biopsy, routine radiography, tomography, and sonography when appropriate. In 10 patients, CT identified tumors that had not been apparent clinically; eight of these were in the nasopharynx and two in the hypopharynx. In another 26 patients, CT showed the tumor to be more locally extensive than had been evident clinically; 12 of these tumors were in the oropharynx. A new technique of CT-guided biopsy of head and neck tumors was used in 20 patients to attain histologic information or to confirm the extent of the tumor. Thus, information obtained by CT scanning or CT-guided biopsy significantly altered treatment planning in 36 of the 100 patients.