Participants will have an ear, nose, and throat examination to determine if they have occult or symptomatic NPC. Their levels of EBV antibody at the time of initial recruitment will be correlated with NPC detection in the period between initial recruitment and the present study. Participants will also be asked to complete a brief risk factor questionnaire and to donate blood, saliva, a nasopharyngeal swab, nasopharyngeal tissue, and urine for future studies.