PIP: Information was gathered on the smoking habits of 187,783 white men between the ages of 50 and 69 between January 1 and May 31, 1952. The men were subsequently traced through October 31, 1955. 11,870 men died during this period. The total experience covered 667,753 man years. For microscopically proved cases of cancer and for the total cases reported as cancer it was found that the death rates were higher among regular cigarette smokers than among men who never smoked, that the mortality ratio increased with the number of cigarettes smoked each day, and that the death rates were higher among pipe and cigar smokers than among men who never smoked. 7316 deaths occurred among regular cigarette smokers; this was an excess of 2665 over the 4651 deaths that would have occurred had the age-specific death rates for smokers been equal to that for nonsmokers. Coronary disease accounted for 52.1% of the excess; lung cancer accounted for 13.5% of the excess; and cancer of other sites accounted for 13.5% of the excess. An extremely high association between cigarette smoking and death rates for men with lung cancer was found in both rural areas and large cities. Only 338 deaths were ascribed to pulmonary diseases other than lung cancer. Only 1120 (9.4%) of the 11,870 deaths were attributed to diseases other than cancer, cardiac, circulatory, and pulmonary diseases and accidents, violence, and suicide. Only 3 of the specific disease entities - gastric and duodenal ulcers and cirrhosis of the liver - showed a statistically significant degree of association with smoking habits. The most important finding of this study was the high degree of association between cigarette smoking and the total death rate.