Parvovirus B19, the only known human pathogenic parvovirus, is highly tropic to human bone marrow and replicates only in erythroid progenitor cells. The basis of this erythroid tropism is the tissue distribution of the B19 cellular receptor, globoside (blood group P antigen). In individuals with underlying hemolytic disorders, infection with parvovirus B19 is the primary cause of transient aplastic crisis (TAC). In immunocompromised patients, persistent B19 infection may develop that manifests as pure red cell aplasia and chronic anemia. B19 infection in utero can result in fetal death, hydrops fetalis, or congenital anemia. Diagnosis is based on examination of the bone marrow and B19 virological studies. Treatment of persistent infection with immunoglobulin leads to a rapid marked resolution of the anemia.