Epidemiological studies and clinical data confirm that occupational exposure to carcinogenic agents plays an important role in cancer etiology. Recent tremendous progress in understanding of the mechanisms of carcinogenesis, and also introduction of new tests to recognize changes occurring in the exposed organism have made it possible for the occupational medicine to detect the earliest cancer stages which occur during the latent phase of the disease. Detecting pre-neoplastic changes which precede an overt form of cancer and identification of measurable indicators of those changes has been one of the fundamental aims of molecular biology research. Biomarkers may serve as a research tool which makes it possible to achieve this aim. Suitably selected biomarker sets can provide information on the extent of the exposure to carcinogenic agents (biomarkers of exposure), detect early changes produced by the agents in the exposed organism (biomarkers of effects), and identify people with particularly high cancer risk (biomarkers of susceptibility). It will soon be possible to use molecular biomarkers, capable of detecting increased cancer risk at the molecular level of cell structure, in prophylactic action intended to reduce cancer incidence. Molecular biomarkers are capable of recording very early health effects of exposure to carcinogens, thus making it possible to determine cancer risk at a very early stage of cancer development.