Sinonasal non-Hodgkin's lymphomas (SNHL) of B- or T-cell immunophenotype have been associated with the Epstein-Barr virus (EBV) in Asian patients. We investigated eight sinonasal and 10 Waldeyer's ring NHL from Western patients for evidence of EBV genomes using a sensitive in situ hybridization technique. EBV DNA was detected in each of three sinonasal NHL with a T-cell immunophenotype and two of five cases with a B-cell immunophenotype. Two of 10 B-cell Waldeyer's ring NHL were positive for EBV genomes. In each positive case, EBV genomes were evenly distributed among the neoplastic cells, whereas no evidence of EBV in associated nonneoplastic lymphocytes or epithelium was seen. The results indicate that B-cell and T-cell sinonasal NHL are associated with EBV in Western as well as in Asian patients, and that EBV may have a role in oncogenesis in NHL of the upper aerodigestive tract. The strong association of EBV with nasopharyngeal carcinoma suggests that the anatomic site is important in the development of EBV-related neoplasms.