Benzene concentrations in urine samples (Cu, ng/L) from 110 workers exposed to benzene in chemical plants and gasoline pumps were determined by injecting urine supernate into a gas chromatograph. The urine was saturated with anhydrous N2SO4to facilitate the passage of benzene in the air over the urine. The solvent was stripped from the urine surface and concentrated on an adsorbent substrate (Carbotrap tube) by means of a suction pump (flow rate 150 ml/m). Wash‐up of the head space was achieved by simultaneous intake of filtered air through charcoal. Benzene was thermi‐cally desorbed and injected in a column (thermal tube desorber, Supelco; 370°C thermal flash; borosilicate capillary glass column SPB‐1, 60 m length, 0.75 mm ID, 1 pm film thickness; GC Dani 8580‐FID). Benzene concentrations in the urine from 40 non‐exposed subjects (20 smokers > 20 cigarettes/d and 20 nonsmokers) were also determined [median value of 790 ng/L (10.17 nmol/L) and 131 ng/L (1.70 nmol/L), respectively]. The 8‐h time‐weighted exposure intensity (Cl, ng/m3) of individual workers was monitored by means of charcoal tubes. The median value for exposure to benzene was 736 ng/m3(9.42 μmol/m3) [geometric standard deviation (CSD) ‐ 2.99; range 64 μg/m3(0.82 μmol/m3) to 13,387 μg/m3) (171.30 μmol/m3)]. The following linear correlation was found between benzene concentrations in urine (Cu, ng/L) and benzene concentrations in the breathing zone (Cl, μg/m3):