Occupational exposure to toluene may be evaluated by the quantification of hippuric acid in urine. However, this metabolite is not exclusive to toluene which may lead to bias in exposure assessment. In this study, urinary hippuric acid was compared to urinary ortho-cresol, another toluene metabolite to assess if the latter is a better biomarker of exposure to the solvent. Urine samples from workers exposed to toluene and from a control population were collected and both metabolites were quantified by HPLC. Validation of analytical methods showed that hippuric acid is unstable and that the analytical assay is not robust. Hippuric acid had highly variable concentrations in both workers and control population and was not related to environmental concentrations of the solvent, showing its limited validity as a biomarker. Ortho-cresol, on the other hand, showed specificity and less variability among the individuals tested. We propose that ortho-cresol is a better predictor of occupational exposure to toluene and that it may be used to avoid false positive determinations when hippuric acid is used as biomarker.