Causes of death among 2,190 deceased operating engineers identified from the 1967 International Union of Operating Engineers death benefit listing were analyzed to determine if there were conditions occurring with unusual frequency that might be indicative of hazardous conditions in the work environment. The most striking finding was a three-fold excess of fatal accidents occurring at places other than the home or resident institution. The increased risk was evident in each of four regions of the country and at all ages under 65. Significant excesses in deaths from lung cancer and intestinal cancer were seen also. Comparative mortality from lung cancer was directly related to age, with the greatest increase (two-fold) occurring after age 75. There was no evidence of a greater than expected frequency of deaths from non-malignant respiratory disease among operating engineers.