Epidemiologic studies have demonstrated a causal relation between smoking of cigarettes and cancer of the lung in man. Women smokers, cigar, and pipe smokers also face an increased risk for lung cancer. Prospective and retrospective studies have found a correlation between smoking of cigarettes, cigars, and pipes and cancer of the oral cavity, larynx, and esophagus and for cigarette smokers increased risks to develop cancer of the pancreas, kidney, and urinary bladder. Dose responses have been established between number of cigarettes smoked and cancer of the respiratory and upper digestive tract. Tobacco chewers face an increased risk for cancer of the mouth and esophagus. Tobacco smoke has induced tumors of the lung in the dogs and of the larynx of hamsters. The particulate matter of the smoke is carcinogenic to the skin of mice and rabbits, and the bronchi and connective tissue of rats. In tobacco smoke were identified tumor initiators, tumor promoters, cocarcinogens and organ specific carcinogens. Chewing tobacco is a tumor promoting agent and contains traces of tobacco specific and carcinogenic nitrosamines. Ten to 15 yr after giving up smoking the ex-smoker faces the same low risk to develop cancer of the upper digestive tract, the lung, the pancreas, and the urinary tract as the nonsmoker. It should be our goal, therefore, to prevent young people from starting the smoking habit and to convince the smoker to quit smoking. So far, we can report no success in terms of decreasing smoking habits among younger people. On the other hand, we can take satisfaction from the fact that antismoking propaganda has had an effect on college educated males, that among the population as a whole, there is a considerable number of exsmokers; that smoking cessation clinics do prove cost effective and if they were to become part of every health care center, they could help a large number of heavy smokers who cannot seem to stop smoking on their own. We can also report that there has been a significant reduction in the tar yield of American cigarettes, a reduction which we hope will continue; that the tumorigenic activity of tobacco as measured in animal studies, has decreased; and that as a consequence of the above, the risk of lung cancer and other tobacco-related cancers among smokers of these cigarettes is lower than in years past. It is unlikely that man will ever be able to inhale smoke components as harmless as unpolluted air, but as long as we have a society which accepts this habit and as long as people find satisfaction in smoking, we must work towards the day when tobacco-related cancers and other diseases will be reduced to a minimum. With the world wide coperation of the scientific community, the Departments of Agriculture, and the tobacco industry, it is our hope that this goal will be achieved.