Eleven men were exposed in an exposure chamber to toluene vapor (3.2 mmol/m3, 4.5 hr) with and without a simultaneous po intake of ethanol (15 mmol/kg body wt). The ethanol was administered 70 to 85 min after the onset of the toluene exposure to achieve maximum concentrations of toluene and ethanol in blood at the same time. During the exposure period the solvent concentrations in inspired and expired air as well as the pulmonary ventilation were determined. The solvent concentrations in blood were measured during and for 3 hr after the exposure period. No effect of ethanol on the pulmonary ventilation could be seen during the exposure period. Ethanol decreased the total uptake as well as the relative uptake of toluene. The maximum toluene concentration in the blood increased from 7.4 to 12.5 mumol/liter in the presence of ethanol and apparent clearance of toluene decreased significantly. Toluene exerted no effect on the uptake and elimination of ethanol in blood. The results indicate an influence of a moderate dose of ethanol on the kinetics of toluene. The distribution and/or elimination of toluene from the blood was inhibited resulting in increased tissue exposure.