Improvements of serological techniques allow seroepidemiologic surveys of cytomegalovirus infections. Intrauterine contamination is not unfrequent (1%) but pathological consequences of these infections in the fetus had only been observed after primary infections of the mother. Infections in the first days of life are frequent. The mother is almost exclusively the source of contaminations. The frequency of these infections is influenced by socio-economic factors. In adolescents and adults, contaminations seem related to closed person to person transmission (sexual behavior, kissing...).