The epidemiology of infection with human T cell leukaemia/lymphoma virus (HTLV) types I and II in England and Wales between 1986 and 1992 has been studied. Two sources of data have been reviewed: reports of cases of infection received by the PHLS Communicable Disease Surveillance Centre, and information about people infected with HTLV-I and II provided on laboratory request forms sent to the Virus Reference Division of the PHLS Central Public Health Laboratory. Most patients were of Caribbean origin. The age and sex distribution of people with disease associated with HTLV-I and II in England and Wales resembles that previously recorded in the Caribbean. The data suggest that the prevalence of disease associated with HTLV infection is low in England and Wales, but case ascertainment may be incomplete.