It has been our experience, over a period of years, that most patients with a cardiac disorder, including those with disease of the coronary arteries, can smoke moderately without apparent harm. In fact, for many, smoking not only affords pleasure but aids in promoting emotional stability. Yet it is common practice to advise patients with cardiac disease to abstain from the use of tobacco. Recently, a report was made of the effects of the intravenous injection of nicotine on the circulation.1It was shown that variations in response were as large in normal persons as in those with cardiovascular disease, and that they depended to a greater extent on individual susceptibility than on the presence of disease. In the present study, observations were made on the effects of smoking regular and commercially "denicotinized" cigarets. The indexes used were changes in cardiac output as determined by the ballistocardiograph, changes in