In this study, groups exposed to toluene either intentionally (glue sniffers) or unintentionally (shoe-workers) were compared. The groups were evaluated in terms of urinary levels of the toluene metabolites hippuric acid and o-cresol. Results were also compared with control values. Hippuric acid levels were determined by high performance liquid chromatography and o-cresol levels by gas liquid chromatography. The levels of hippuric acid and o-cresol were found to be statistically significantly higher in glue sniffers than in shoe-workers (p < 0.001) or controls (p < 0.001). In addition, the differences between the levels of urinary hippuric acid and o-cresol in the shoe-workers and in the controls were statistically significant (p < 0.05 and p < 0.001, respectively). These results suggest that extremely high levels of urinary hippuric acid and o-cresol indicate massive exposure to toluene.