This article presents a review of reference values for organic solvent biomarkers. Some of these results were obtained in the research activities of the Italian Society Reference Values (SIVR). Most experiences show data obtained from control groups during occupational exposures assessment investigations. We considered only data related to the following biomarkers: immodified solvents in blood and urine, their main urinary metabolites. The reference values of the following solvents are reported: benzene, toluene, xylene, nhexane, cyclohexane, trichloroethylene, perchloroethylene, methanol, acetone, N,N-dimethylformamide, carbon disulphide. In the text also the influence of some confounding factors is discussed.