A population-based case-control study of nasopharyngeal cancer is proposed to: a) determine if occupational and residential exposure to formaldehyde increases the risk of nasopharyngeal cancer, and b) identify other medical, environmental and lifestyle factors associated with the disease in a low-incidence population. Eligible cases will be all persons aged 18-74 years who develop nasopharyngeal cancer between January 1, 1987 and June 30, 1991, and who reside in areas covered by six population-based cancer registries in the United States funded by the Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute. A random digit dialing technique will be used to select one control per case from among residents of the same areas in which the cases reside. Subjects will be interviewed by phone to determine their occupational and residential histories, along with other factors suspected to be associated with risk of nasopharyngeal cancer, including medical, tobacco, alcohol and dietary histories. Using exposure assessment methods already developed in a preliminary study, we will calculate indices of formaldehyde exposure both from home and workplace sources. Data processing and analysis will be performed at a coordinating center in Seattle. Both stratified and multivariate analysis will be used to estimate relative risks of nasopharyngeal cancer in relation to the various environmental factors considered.