Subjects occupationally exposed to potential mutagens/carcinogens represent the most suitable groups for epidemiological studies aimed at assessing the risk for the individual or the offspring. Several cancer risks to humans have been detected by epidemiological studies performed in occupational settings. Cancer epidemiology studies have been able (a) to identify specific occupations or agents associated with the risk; (b) to verify the results of experimental studies; (c) to test the effectiveness of changes in production or preventive measures in decreasing risks. Reproductive epidemiology has suggested a risk of spontaneous abortions or of malformation in the offspring of workers exposed to some chemicals or occupations, but data are often conflicting due to methodological problems. With the aim of early assessment of risk in mind, the epidemiological use of indicators of exposure or of the early effect of exposure to genotoxic agents is increasingly applied to occupational groups. Cytological monitoring of subjects at risk of occupational cancer of lung or bladder is carried out mainly to diagnose precancerous lesions of target tissues. Cytogenetic methods (chromosome aberrations, SCE, micronuclei) in somatic cells provide a means for detecting early effects of occupational exposure to known or potential mutagens/carcinogens in selected groups of individuals, but their significance is widely debated. Monitoring of urinary mutagenicity, as applied in nurses handling cytostatic drugs, is an example of how an indicator of exposure to genotoxins can be used to evaluate the impact of preventive measures. Among the perspectives, biochemical epidemiology seems to be promising in detecting individuals genetically susceptible to cancer.