A study was conducted to determine if there were any health effects among the polythene printers who were exposed to toluene and to evaluate the use of urinary hippuric acid in biological monitoring. The study covered 54 printers from 6 plants out of the universe population of 32 polythene printing plants who used toluene as ink dilutants. They were matched with 54 controls for age, sex, race and similar occupational status. All were interviewed and examined clinically. 23 patients were selected for neurobehavioural tests. 26% of the printers had more than 10 years of exposure to toluene. No case of clinical encephalopathy or peripheral neuropathy was detected. 38.9% of the printers had hand dermatitis compared with 1.9% among the controls. Results of the neurobehavioural tests for the 23 printers were not statistically different from the controls. The results of the liver function test were within normal limits. The mean toluene-in-air level was 246 +/- 25 mg/m. Mean blood toluene was 0.63 +/- 0.14 microgram/ml. The mean urinary hippuric acid was 2.83 +/- 0.48 mg/ml as compared to 0.35 +/- 0.08 mg/ml in the controls. Urine hippuric acid corrected to SG of 1.016 was well correlated to air toluene level (r = 0.81). Toluene appears not to have any significant nervous system or liver effects in these printers. Urinary hippuric acid is a useful indicator for biological monitoring of atmospheric exposure to toluene.