A prospective serological study was undertaken in hospital personnel who care for Lassa fever (LF) patients in an endemic region of Sierra Leone, West Africa. Among personnel from three hospitals where barrier nursing is practised, antibody prevalence and seroconversion by age and sex were consistently equal to or lower than those of persons in nearby village populations. No group among hospital personnel evaluated by age, sex, contact, or occupational exposure was at higher risk than another. Hospital staff in Sierra Leone who care for LF patients using simple barrier nursing methods have no higher risk of infection than the local population. These findings support the proposal that patients with LF in non-endemic countries need not be confined to isolators.