Antismoking education campaigns in out society have met with only partial success: today 55 to 60 million Americans smoke, and the habit is increasing among teenagers and women. It is important to protect individuals who continue to smoke despite all warnings. There is evidence that this can be accomplished in at least two ways. First, it may be possible to remove toxic smoke components and thus reduce specific hazards. Second, the doseresponse evidence suggests that, if the total intake of smoke can be reduced, after an appropriate time a reduction in disease incidence should occur. The technology to achieve these results has been developed and can be applied to the manufacture of commercial cigarettes. These cigarettes will not conform to traditional flavour patterns, but consumer perception can be made to change and compensating flavours and fragrances can be added. The feasibility of less hazardous cigarettes raises the question of whether there are limits of cigarette and smoke composition that may approach relative safety. These limits can be defined as the smoke intake doses at which the risk of disease in smokers approaches that in nonsmokers. Such values can be extimated by dose-response analysis of several epidemiological studies and by extrapolation of blood concentrations at different rates of intake for certain smoke components, such as carbon monoxide. Critical values determined by these methods should not be interpreted as indicators of safe smoking levels; they do imply, however, that a rapid shift in cigarette consumption habits toward the proposed range of values will make possible a substantial reduction in the current epidemic proportions of smoking-related diseases.