In this study, antibody levels to Epstein-Barr virus (EBV) capsid antigen (VCA) and EBV early antigens (EA) were analysed by enzyme immunoassay in 54 newly diagnosed type 1 diabetic children and in matched controls. The patients had significantly lower EBV VCA IgG-class antibody levels (p less than 0.02). This was true particularly in young patients and in boys (p less than 0.005). VCA IgA-class antibody levels were also decreased in young patients (p less than 0.02). VCA IgM-class antibodies were observed in two of the patients only. IgG- and IgA-class antibodies to EBV EA or rubella virus antigen showed no differences between patients and controls. The results suggest that EBV infections coincide with the onset of clinical diabetes relatively rarely. However, the abnormally low antibody response to EBV VCA in diabetic children suggests abnormalities in the EBV-specific immune response.