AIMS/HYPOTHESIS: Type 1 diabetes is an autoimmune disease resulting from a complex interplay between genetic and environmental factors. Cytomegalovirus (CMV) infection is one of the environmental factors implicated in the development of type 1 diabetes, although the association remains unproven. We aimed to clarify the possible correlation between CMV infections and type 1 diabetes-associated autoimmunity at the time point of autoantibody appearance in young children with HLA-conferred disease susceptibility. METHODS: CMV-specific IgG antibodies were analysed from serum samples of 169 children who had developed the first type 1 diabetes-associated autoantibody by the age of 2 years and who turned positive for multiple autoantibodies during later follow-up. We also studied 791 control children matched for sex, age and HLA genotype. The subsequent progression to clinical diabetes was analysed. The serum specimens used were collected at the time of autoantibody seroconversion or within the next 6 months. RESULTS: The frequency of CMV antibodies was similar in both study groups at the time of the first autoantibody appearance. Of the index children, 38 (22.5%) were CMV IgG antibody-positive, while the figure for control children was 206 (26.0%; p = 0.38). No association between perinatal CMV infection and progression to type 1 diabetes was observed. CONCLUSIONS/INTERPRETATION: According to these results, perinatal CMV infections are not associated with early serological signs of beta cell autoimmunity or progression to type 1 diabetes in children with diabetes risk-associated HLA genotype.