This study was designed to investigate the hemodynamic effects of smoking in patients with congestive heart failure. Hemodynamic measurements were made in seven patients with heart failure before, during, and after smoking two unfiltered cigarettes (approximately 2.4 mg of nicotine). Smoking significantly (p less than .05) increased heart rate and decreased stroke volume. Cardiac output remained unchanged. Significant increases were noted in systemic systolic and diastolic blood pressures concomitant with significant increases in total systemic vascular resistance and systemic arteriolar resistance. Pulmonary arterial pressure and total pulmonary vascular resistance increased as well. Mean right atrial pressure and pulmonary capillary wedge pressure rose modestly during smoking. Finally, the double product, an index of myocardial oxygen consumption, increased considerably during the smoking and postsmoking periods. Smoking elicits significant hemodynamic effects in patients with congestive heart failure, many unfavorable and potentially detrimental.