The oxidative stress plays an important role in certain pathologies, notably in carcinogenesis. Indeed, reactive oxygen species (ROS) can induce a variety of damage to DNA, including oxidized bases which will then be repaired and eliminated in urine. The 8-hydroxy-2'-deoxyguanosine (8-OHdG), the most frequent member of these oxidized bases, can be measured in DNA or in urine by various methods. The urinary measurement was used in several studies among subjects with occupational or environmental exposure. Diverse chemical or physical agents can indeed contribute to the increase of oxidative stress, although the latter has several origins. Our objective is to analyze through these studies the interest, the limits and the implementation of this biomarker. The majority of the studies reveal an increase of the concentration of 8-OHdG in urine in exposed subjects (polycyclic aromatic hydrocarbons, metals, ionizing radiation and other agents) compared with controls or according to exposure levels. The urinary concentration of 8-OHdG is subject to important inter and intra-individual variations. The biomonitoring studies have to take into account diverse confounding factors, which may have conflicting effects. Moreover the results strongly depend on the analytical method used. Thus other investigations are necessary to validate this biomarker and better know its sources of variability, its biological significance, its dose-response relationship and its kinetics after exposure to oxidative stress agents.