To estimate the quantitative relation between exposure to airborne n-hexane and various markers of immune function, 35 male workers were examined and compared with unexposed controls. 2. Urinary 2,5-hexanedione concentrations were significantly higher in the exposed group than in the unexposed. 3. A significant suppression was observed in the serum immunoglobulin (IgG, IgM and IgA) levels between two populations. Also, a significant correlation was found between urinary 2,5-hexanedione concentrations and serum Ig level of the exposed group. 4. No significant difference between white blood cell counts was found in the two groups.