Purpose: The aim of the present study was to clarify effects of long term, low-level monocyclic aromatic hydrocarbons exposure (MAHs) such as styrene, toluene and xylene on physiological levels of epinephrine (EP) and norepinephrine (NEP) and these hormones influences diagnosis indices of metabolic syndrome (MetS). Methods: Blood pressure and serum biochemical parameters were measured using digital sphygmomanometer and autochemical analyzer. EP and NEP were analyzed by using ELISA kit and exposure level of MAHs was measured by NIOSH method. Results: The differences of general characteristics such as age, smoking and drinking habits in both groups were not significantly different except working hours per day. In exposed workers, exposure levels of MAHs showed very low concentrations. Serum HDL-cholesterol concentration was significantly higher in exposed group, but concentration of NEP was significantly higher in control group. On multiple logistic regression analysis for the diagnosis indices of MetS, EP was WC (OR=0.970), NEP was blood pressure (OR=1.002) and MAHs exposure were significantly associated with HDL-cholesterol (OR=0.257), fasting glucose (OR=3.028) and MetS (OR=0.372). Conclusion: These findings suggest that the chronic exposure of low level MAHs maycontribute to glucose metabolism and induction of MetS. And also, changes of EP and NEP levels by exposure of MAHs affect blood pressure.