This study summarizes the effects of both the rate and the cumulative dose of cigarette smoking on the health of the original Framingham cohort, 5209 individuals aged 30 to 62 years at entry. After 34 years of follow-up, it was observed that cigarette smoking was the prime determinant of chronic cough, and reduced both forced vital capacity and the 1-second forced expiratory volume. A significant relationship was observed between cigarette smoking and the incidence of cancer of the lung, stroke and transient ischemic attacks, intermittent claudication, and total cardiovascular disease, and most especially the average annual death rate. Cigarette smoking was significantly related to coronary heart disease in men 45 to 64 years old, although not related in women or older men. The data confirm and extend the evidence of the detrimental influence of cigarette smoking on health.