Ethylene oxide is widely used to sterilize heat-sensitive materials in hospital. Previous reports for neurotoxic effects of ethylene oxide have been described in animals and humans. To assess the exposure level and neurobehavioral effect of ethylene oxide, a cross-sectional study was performed to 27 nurses from central supply unit at hospital, exposed to ethylene oxide and 32 nurses as reference. Ethylene oxide was collected with using a personal air sampler and analyzed by gas chromatography for the determination of exposure level, and five items among Neurobehavioral Core Test Battery (NCTB) of World Health Organization, including Digit Span, Benton visual retention. Santa Ana dexterity, Digit Symbol and Simple reaction time, were administered to the exposed and reference group. The mean exposure level was 0.63 ppm in the exposed group and six subjects were exposed above the level of 1 ppm, which is currently regulated by the Korean Ministry of Labor. The results of neurobehavioral test in the exposed group showed significantly poorer performances in Digit Span forward and backward, Benton visual retention and Simple reaction time, comparing with the reference group. When the exposure level was divided into below and above the level of 1 ppm, there were significant differences in performance on Benton visual retentions, Digit Symbol and Simple reaction time. Also, Digit Span forward and backward showed significantly poorer performances below the level of 1 ppm, compared with reference group. Simple reaction time was still significantly delayed by the exposure level after controlling the confounding factors with multiple regression analysis. The results suggest that the periodic measurement of ethylene oxide in hospital and health care program is needed.