The occupation of fire fighting is alleged to be associated with an increased risk of death from circulatory disease, but not all mortality studies confirm this finding. An historical prospective study was done in the Toronto Fire Department to examine the relationship between fire fighting and mortality from coronary artery disease. Using adjusted city of Toronto rates for comparison, the overall standardized mortality ratio (SMR) for fire fighters aged 45 to 54 was 1.73 (P less than .005). Stratification by age and year of death produced the highest SMR of 2.47 (P less than .10) in fire fighters aged 45 to 49 during the period 1975 to 1979. A relative index of fire fighting activity was created and tested but proved difficult to use in an historic study. Explanations are offered and recommendations for further studies are made.