To study the influence of cigarette smoking on the toxicokinetics of toluene, 10 habitual smokers who intended to stop smoking were exposed to toluene vapor (3.2 mmol/m ³ , 4 h) at three different exposure occasions: (I) while the smoking habit was still ongoing, and (II and III) 1 and 3–4 wk, respectively, after the day at which the smoking habit was discontinued. Solvent concentrations in the exhaled air and in the blood as well as hippuric acid concentrations in the urine were measured during the exposure period and for 3 h after the exposure period. The apparent clearance of toluene decreased significantly (p < 0.05) 3–4 wk after the smoking habit was discontinued. This decrease was not a consequence of the increased body weight noticed in the subjects. No statistically significant differences between the three exposure occasions in the elimination rate of hippuric acid could be demonstrated. Thus, cigarette smoking seems to enhance the elimination rate of toluene from the body, since the apparent clearance was decreased after smoking was stopped.