Fire fighters are exposed to substances which are recognized or suspected causal agents in cancer or heart disease. The purpose of this study was to determine whether or not fire fighters experience increased risk for any specific cause of death. A retrospective cohort study was conducted, with 5,995 subjects recruited from all six fire departments within Metropolitan Toronto. The mortality experience of the cohort was ascertained through computerized record linkage and compared to that of the male Ontario population specific to cause, age, and calendar period from 1950 through 1989. Average duration of follow-up was 21 years, and there were 777 deaths among the 5,414 males included in the analysis, giving an all-cause standardized mortality ratio of 95 (95% confidence interval: 88-102). Three specific causes of death exhibit statistically significant excesses (brain tumors, "other" malignant neoplasms, and aortic aneurysms). There are also slight increases in risk for some other sites of cancer, and for various diseases of the respiratory, circulatory, and digestive systems. This study is consistent with others in demonstrating that fire fighters experience increased risk of death from cancer of the brain, and in suggesting increased risk for various other causes of death.