In response to a request for a health hazard evaluation, NIOSH investigators conducted an evaluation of health care worker exposure to ribavirin (36791045) in relation to engineering controls, work practices, and method of administration. Personal air monitoring for aerosolized ribavirin (AR) was carried out in conjunction with the following administration methods: ICN Aerosol Delivery Hood (ADH) with ICN evaluation device in operation, ADH enclosed by the Demistifier scavenging tent, croup tent, and direct coupling to a ventilator. Personal samples were collected in the workers' breathing zone. Exposures to personnel were greatest when ribavirin was administered using the croup tent, less with the ADH, and least with the ventilator or ADH in conjunction with a scavenging tent. Full shift breathing zone concentrations among nurses were related to the amount of time spent in the treatment room, which depended on the severity of the patient's illness and number of children treated at a time. Recommendations were offered for lowering the exposure levels.