Parvovirus B19 is the aetiological agent of one of the classical diseases of childhood, the rash illness fifth disease (erythema infectiosum). Beside this usually harmless illness parvovirus B19 was, however, found to be associated with a variety of severe diseases, mainly arthritis, anemia, thrombo- and granulocytopenia, hepatitis and myocarditis. In these cases parvovirus B19 may persist over long periods of time in the peripheral blood or in individual organs of the patients. During pregnancy B19-infections may result in spontaneous abortions, hydrops fetalis, and intrauterine fetal death. The detection of viral DNA and antibodies in the maternal serum and precise ultrasound surveillance of the allows an early diagnosis of the development of hydropic symptoms in the fetus. In most cases in time intrauterine blood transfusions result in the birth of sound children. Since about half of the young adults are not immunologically protected parvovirus B19-infections should be assumed as an important reason for virus-correlated problems during pregnancy. Based on these epidemiological data that were accumulated during the past years clinicians should pay more attention to B19-infections and the mode of viral transmission.