Of 6054 people who had high titres of antibodies against the viral capsid antigen of Epstein-Barr virus but no symptoms or signs of nasopharyngeal carcinoma as assessed by conventional methods, 130 were randomly recruited and examined by fibreoptic endoscopy and biopsy of several sites of the nasopharynx. 7 cases of nasopharyngeal carcinoma were detected. The tumours were largely confined to the pharyngeal recess, which suggests that it is the area of the nasopharynx most prone to the development of the tumour. Tumour was found in both recesses in 1 subject, who also had evidence of transition from severe epithelial dysplasia to carcinoma in a sample from the left roof, which suggests that the disease was multifocal in origin. This study showed that endoscopy and biopsy of several sites of the nasopharynx are more effective than the conventional approach in the detection of subclinical nasopharyngeal carcinoma among seropositive individuals at high risk of the disorder.