Human parvovirus B19 is a common infection that causes a number of clinical illnesses, most of which are benign. However, in patients with a need for increased red cell production, a deficient immune system, or both (such as occurs in the fetus), it can be a life-threatening infection. Intravenous immunoglobulin should be considered in the treatment of chronic B19 infection in immunodeficient patients and possibly in the management of other serious B19 infections. Recent advances in the laboratory, especially the increased sensitivity of polymerase chain reaction assay for detecting B19 DNA and the development of a cell line that produces B19 proteins in the form of empty capsids, should lead to significant advances in our understanding, treatment, and management of B19 disease in the near future.