We compared 50 patients with head and neck squamous cell carcinomas (cases) and 45 matched healthy controls. Biopsy specimens were taken from tumours and normal tissue of the cases and controls respectively and serial paraffin embedded sections were processed to detect Epstein-Barr (EB) viral antigen. We found EB viral proteins in 38% of cases and none in controls, which suggests a positive correlation. Serum samples were also tested for the presence of EB virus IgG by ELISA for comparison with immunohistochemical findings. Patients with positive immunohistochemical staining results had significantly higher mean antibody titres compared with those with negative results. ELISA may be useful in determining the etiology of head and neck cancers, but the results are not unequivocally reliable.