Influence of combined exposure to solvent vapours on the metabolism of m-xylene and the kinetics of excretion of methylbenzoic acid (MBA) in urine was investigated. The volunteers were exposed in groups of four or five. Each experiment consisted of two parts. During the first part, the same test group was exposed to m-xylene for a period of 4 hours, whereas during the second part, the group was exposed to m-xylene in combination with other solvents. No significant differences in the excretion of MBA in urine were observed after exposure to m-xylene in concentrations of about 45 and 70 ppm and exposure to m-xylene together with n-hexane, toluene, methyl isobutyl ketone or n-butyl alcohol in combined concentrations of about 90 and 140 ppm. Only in the case of combined exposure to m-xylene and n-butyl acetate was a significant increase in the excretion of MBA in urine found. For both the single and combined exposure to kinetics of excretion of MBA was similar with t1/2 values in the first phase of excretion ranging between 1-1.3 h.