To estimate the quantitative relation between chronic co-exposure to airborne n-hexane, toluen, methyl ethyl ketone (MEK) and various markers of immune function such as proliferative response of peripheral blood lymphocytes and lymphocyte subpopulations, a group of workers employed in a shoe factory were examined and compared with the unexposed controls. A significant increase was observed in the proliferative response of the peripheral lymphocytes to 2.5 and 5 mu g PHA in the exposed group compared with that of the control group. There was no significant change in the percentage of circulating CD3(+), CD4(+) CD8(+), CD19(+), CD16(+) lymphocytes even in those workers with 3.3-fold higher mean levels of urine 2,5-hexanedione (2,5-Hxdn) and approximately twofold higher mean levels of urine hippuric acid (HA) as compared to controls. No difference was also observed between the mean granulocyte, monocyte, lymphocyte: percentages of the groups, but a significant increase was observed in mean serum C3 level of the workers. Our results suggest that while lymphocyte subpopulations and leucocyte percentages are not affected, the proliferative response of the peripheral lymphocytes is stimulated after chronic co-exposure to n-hexane, toluen and MEK at the defined levels. (C) 1999 Published by Elsevier Science B.V. All rights reserved.