Estimates were made of lung cancer mortality risks during 1959 through 1975 in a cohort of silicotic metal miners who were diagnosed for silicosis in 1959 through 1961. Lung cancer mortality was increased in silicotics, standard mortality ratio (SMR) 1.73, but did not reach statistical significance. Lung cancer SMRs were higher in silicotics than in nonsilicotics, even in most subgroups, after tabulating by cigarette smoking habit, years service in an underground metal mine, type of ore mined, radon (10043922) exposure group, or year of hire. SRMs were significantly increased in silicotics and nonsilicotics who were current smokers in 1959 through 1961, particularly in those who had smoked cigarettes for more than 25 years. SMRs were also significantly increased in nonsilicotics (1.152) who had worked in excess of 20 years in an underground metal mine and in silicotics (14.03) and nonsilicotics (2.66) who had been employed at a mercury mine. The age adjusted lung cancer risk in silicotics was 1.56 times higher than that in nonsilicotics. The age and smoking adjusted lung cancer risk in silicotics was 1.96 times higher than that in nonsilicotics. The age adjusted lung cancer risk in silicotics who were employed in mines were there was low radon exposure was 1.90 times higher than in nonsilicotics and the age and smoking adjusted risk was 2.59. Silicosis and the interaction between silicosis and cigarette smoking habits were not statistically significant factors related to lung cancer mortality.