This study was undertaken to determine whether a specific group of hospital workers exposed to ethylene oxide (ETO) in sterilizing areas showed evidence of increased levels of sister chromatid exchange (SCE) formation. SCE frequencies were determined for 14 sterilizer workers and 14 matched controls. Time-weighted average (TWA) and peak ambient levels of ETO were measured in the sterilizing areas. Results indicated that all sterilizer workers were exposed to less than 5 parts per million TWA of ETO and that there were no statistically significant differences in SCE levels between sterilizer workers and controls. Smoking habits did appear to be associated with increased SCE levels. In this particular hospital setting no evidence of genetic effects stemming from employees' exposure to low levels of ETO was found.