A NIOSH investigation was undertaken to evaluate ethylene-oxide (75218) (EtO) exposure among employees in the central supply (CS) area of a Midwestern hospital. Personal breathing zone, area concentration, and air samples were collected during the field surveys from April to December 1985, and analyzed for organic components via gas chromatography. Leak sources and ventilation systems were also assessed. Questionnaires were administered to 12 CS employees for an evaluation of symptoms associated with EtO exposure. The workers reported headaches, dizziness, mucous membrane irritation, vomiting, and smelling a sweet odor during a portion of the operating cycle of the sterilizers. Time weighted averages for personal exposure concentrations for EtO ranged from 0.23 to 0.56 parts per million (ppm) among CS employees. Short term area concentrations of up to 77ppm were noted at breathing zone height in the cart wash area. Area air concentrations of less than 0.1ppm were noted for hydrochloric-acid (7647010), less than 0.2ppm for chlorine (7782505), less than 5.0ppm for carbon-monoxide (630080), and up to 700ppm for carbon-dioxide (124389). The existing ventilation system had insufficient flow capacity at the point of connection. Some of the EtO exhausted from the large sterilizer was found to be forced into the cart wash area. A follow up survey 1 year later indicated the initiation of effective changes and modifications to minimize employee exposure; employees had not suffered from EtO symptoms. The authors conclude that the workers have been exposed to hazardous levels of the compound, stress the importance of short term exposure criteria, and offer further recommendations for EtO sterilization units.