Isolation of human herpesvirus-7 (HHV-7) was first reported in 1990. The virus was iso-lated from activated CD4+ T lymphocytes of a healthy individual. The CD4 molecule ap-pears to be a receptor for virus attachment. HHV-7 is distinct from all other known hu-man herpesviruses but is most closely related to HHV-6 and CMV and is in the subfamily with these two viruses. Seroepidemiologic studies indicate that this virus usu-ally does not infect children until after infancy but that nearly 90% of children are anti-body positive by 3 years of age. As with HHV-6, this virus is frequently isolated from saliva, and close personal contact is the probable means of transmission. Also, like HHV-6, this virus may be a cause of exanthem subitum. The diagnosis of acute infection can be made by the demonstration of seroconversion. No treatment has been identified.