Human parvovirus B19 has been associated with disease only for the past few years. First isolated from sera obtained for studies on hepatitis B in 1975, it was not until 1981 that infection with this small, single-stranded DNA virus was related to aplastic crisis associated with hemolytic anemia. A nonspecific viral prodrome, the occurrence in family members, and epidemics of aplastic crisis suggested the infectious etiology. Human parvovirus infection has since been associated with arthritis, erythema infectiosum (fifth disease), fetal death, and hydrops fetalis. Through the use of recently developed serologic tests, epidemics of erythema infectiosum and parvoviral infection have been related not only to aplastic crisis but also to intrauterine infection and hydrops; DNA hybridization studies have allowed the detection of viral DNA in serum and tissue extracts. Studies have been hampered by the lack of an ability to culture the virus, but this is now possible utilizing bone marrow culture and erythropoietin. This article is a historical and clinical review of human parvovirus infection and disease and considers potential questions regarding their consequences.