AIM--To investigate whether non-Hodgkin's lymphomas arising in the sinonasal region or Waldeyer's ring contain the Epstein-Barr virus (EBV) genome in lesional tissue. METHOD--Sections from paraffin wax blocks of 22 lymphoid proliferations arising in the sinonasal region or Waldeyer's ring were studied with EBV encoded RNAs (EBER-1 and -2) using in situ hybridisation. RESULTS--EBV was detected in nuclei of tumour cells of five of seven T cell lymphomas and in nuclei of two of seven diffuse, large cell immunoblastic lymphomas of B phenotype in the sinonasal region. Of tumours arising in Waldeyer's ring, two of 10 non-Hodgkin's lymphomas (both large cell) were positive, as was a single case of Hodgkin's disease. Lymphoma of other types, including Western type Burkitt's lymphoma, and nodular and diffuse small cleaved cell lymphoma, were negative. CONCLUSION--EBV is highly associated with large cell lymphomas especially T cell lymphomas of sinonasal origin in the indigenous Irish population, underlining the importance of this virus in nasopharyngeal lymphomas in Northern European as well as Asian populations.