Hypertension is a powerful independent contributor to cardiovascular morbidity and mortality, on average conferring a threefold increase in risk at all ages and in both sexes. Coronary heart disease is now the chief lethal sequela of hypertension, occurring at a rate two to three times higher in hypertensives than in normotensives. The risk of cardiovascular morbidity and mortality is also greatly affected by cigarette smoking. For each 10 cigarettes per day there is an incremental increase in cardiovascular mortality in men (18%) and in women (31%). The risk of coronary heart disease that is associated with hypertension varies over an eightfold range depending on coexistent risk factors. Smoking increases the cardiovascular risk, at any level of blood pressure, for coronary heart disease, stroke and cardiac failure. The risk of peripheral arterial disease is particularly adversely affected. Trials of antihypertensive therapy to reduce the coronary heart disease risk have yielded disappointing results, very likely because of failure to correct for blood lipids and cigarette smoking. These trials have consistently shown that cigarette smoking has a powerful effect on the risk of coronary heart disease whether the patients were treated for hypertension or not. Data from the Framingham Study have shown a prompt halving of the coronary heart disease risk in those who give up smoking compared to those who continue to smoke, regardless of the duration of the habit. Hypertensives who smoke one pack of cigarettes a day can quickly reduce the risk by 35-40% by not smoking. Switching to filter cigarettes offers no advantage.(ABSTRACT TRUNCATED AT 250 WORDS)