Benzene may be regarded as one of the most hazardous of solvents. Nevertheless, not only in industry and laboratories, but also in several trades and even in “do-it-yourself” jobs benzene is still used, mainly because of its excellent solvent properties and relatively low cost. Less toxic solvents, which may replace benzene, are available, but they are not yet sufficiently used. In addition, some solvents and cleaning agents may contain a considerable admixture of benzene, not presented as such on the label. Diagnosis and prevention of intoxications in and outside industry could be promoted if a practicable method existed for the quantitative measurement of benzene absorption. Sampling of the atmosphere often yields insufficiently reliable data and many samples may have to be analysed; in some cases, the pre-existent exposure may have to be reconstructed. Examination of metabolites in human excreta may yield more adequate data since the body acts as a personal sampler; besides indicating the intake of a certain agent the effects of the agent on the human organism are simultaneously detected. It must be remembered, however, that benzene is metabolised very rapidly. In the case of benzene exposure a biological sampling method can make use of the urinary excretion of the metabolite phenol, a product of oxidative detoxication. The literature of this method contains variable data on normal excretion, relationship with benzene exposure, allowable biological limit values, etc. In this paper possible reasons for these discrepancies will be discussed, and biological limit values will be suggested.