Sera from 28 patients with Primary Sjögren's Syndrome (SS) and 20 healthy subjects were tested for the presence of antibodies to Epstein-Barr Virus (EBV) and Cytomegalovirus (CMV). No difference was noted in the mean titre of anti-CMV antibodies in patients and in controls. For what concerns EBV, the mean titre of anti-EBNA antibodies was significantly higher in SS patients than in normals (p less than 0.001); moreover, within the SS population, titres were higher in SSB-positive than in SSB-negative patients (p less than 0.05). These results, together with the fact that anti-SSB antibodies (characteristic of Sjögren's Syndrome) recognize also two EBV-encoded RNAs, strengthen the hypothesis that EBV is involved in the pathogenesis of SS.