During the last ten years, interest has been focussed on occupational exposure in thermoelectric power plants (i.e., coal dust, polycyclic aromatic hydrocarbons, dioxin, dielectric liquids, PCB's, asbestos, etc.), although available evidence on its effects on the health status of the occupational population are far from being definitive. A retrospective cohort study was carried out to investigate the association between exposure to risk factors and mortality for cancer in three thermoelectric power plants located in the north-east of Italy. The three plants studied started with oil and coal but since 1968 they utilized mostly coal as fuel. In spite of the different fuel used at the beginning, the production process has been fairly constant since the main conversion from oil to coal with a substantial increase in power production. A total of 1,772 male workers were included in the total study cohort and followed-up from 1968 to 1987, with a total of 22,090 person-years of exposure. Eighty percent of the cohort began to work in the plant before 30 years of age, and had a mean period of employment of 9.5 years. The cohort was completely traced to the end of the follow-up period by using an original computer system based on personal fiscal codes. Causes of death were ascertained in the municipalities where the deaths occurred and coded according to the International Classification of Disease, IX Revision. During the study period 68 deaths were observed with an SMR for all causes of death equal to 0.79.(ABSTRACT TRUNCATED AT 250 WORDS)