Despite the knowledge of the link between many sites of cancer occurence and previous occupational exposure, occupational cancers are generally underestimated. These cancers can be prevented through specific plans. In France, the number of cases requesting and receiving compensation for occupational cancer is increasing. The frequency of occupational exposure to carcinogens was recently evaluated. Legislation was reinforced in order to obtain a better control of exposure to carcinogens in the workplace. Lung cancer is the most frequent of occupational cancers. Epidemiological studies contribute to a better knowledge of etiologies and occupations responsible for the outcome of these cancers and allow quantification of the risk of cancer linked to different situations of exposure. Beside classical epidemiological studies, molecular epidemiology aims at identifying molecular targets of occupational agents. This approach may allow a better knowledge of the part played by occupational agents in these multifactorial diseases.