In Lombardy, the regional project "Prevention of occupational cancers" is ongoing. The main objectives of this project are to identify work environments in which there might be a possible exposure to carcinogenic substances and to elaborate preventive measures. A casual sample of 250 working settings representing the different economic activities has been selected and evaluated. The 10% of the examined workplaces showed a possible exposure to chemical carcinogens. The most common carcinogens were trichloroethylene, preparation of plastics materials containing acrylonitrile-butadiene-stirene, formaldehyde, wood dust, hexavalent chromium, silica and polycyclic aromatic hydrocarbons. Galvanic industries, Bitumen production and placing companies and Plastics processing plants will be studied for environmental and biological monitoring and for the development of preventive measures.