Blood samples from 10 ethene-exposed fruit store workers and 10 referents were analyzed for the level of hydroxyethyl adducts to N-terminal valine in hemoglobin (Hb). A statistically significant difference was obtained between the nonsmoking workers (N = 7) and the nonsmoking referents (N = 6). This finding demonstrates that ethene is metabolized to ethylene oxide in man. According to this preliminary study, ethene exposure at 0.3 (uncertainty range 0.1-1) ppm during work hours increases the adduct level by 23 pmol/g Hb. This figure is compatible with a metabolic conversion of 3% (1-10%) of the inhaled ethene to ethylene oxide.