Fiberoptic endoscopic examination and biopsy of the nasopharynx was done in 130 patients as a prospective study. They all had elevated titers of antibodies against the viral capsid antigen of Epstein-Barr virus but no symptoms or signs of nasopharyngeal carcinoma. Each underwent a biopsy from six fixed sites in the nasopharynx. Of the 780 biopsy specimens taken from seven patients, 11 showed the presence of nasopharyngeal carcinoma. Techniques to improve the yields of such biopsies with fiberoptic endoscopy are discussed. The presence of tumor was unrelated to the macroscopic endoscopic findings. The highest incidence of subclinical tumor is in the pharyngeal recess.