Parvovirus B19 is a common source of infection with a seroprevalence of 60-70 per cent in the adult population. The most common manifestation is erythema infectiosum ('fifth disease'), with exanthem, fever and upper airway symptoms in children. The infection can give rise to a multifacetted clinical picture and is probably underdiagnosed, particularly in risk groups (individuals with haemolytic anaemia or immunosuppression, and fetuses). Serological diagnosis can now be complemented with the demonstration of viral DNA using the PCR (polymerase chain reaction) test in various body fluids, or tissue biopsy. Recent years have witnessed manifest increase in clinical knowledge of parvovirus B19-associated complications, and their diagnosis and treatment.