Although the hemodynamic changes produced by small doses of nalbuphine given to patients with cardiac disease are minimal, the cardiovascular effects of large doses which have been used as supplements for general anesthesia have not been investigated. Cardiovascular variables were measured after incremental doses of nalbuphine, up to 2 or 3 mg/kg in fourteen patients with coronary artery disease with normal left ventricular function and in seven patients with mitral valve disease. No significant changes in cardiac index, stroke work index, mean arterial pressure, pulmonary diastolic or wedge pressure, heart rate, or central venous pressure occurred in the preoperative period. However, nalbuphine alone did not produce surgical anesthesia and the addition of diazepam, nitrous oxide, or halothane was required in all patients. The addition of halothane coupled with surgical stimulation significantly decreased cardiac and stroke indices, increased mean arterial and pulmonary wedge pressures, and increased systemic vascular resistance in patients with coronary artery disease. In patients with mitral valve disease, following surgical incision, there were small but significant decreases in cardiac index and left ventricular stoke work index, and increases in systemic vascular resistance. Despite its lack of deleterious hemodynamic effects, the place of nalbuphine in the armamentarium of the anesthesiologist must be limited to use as a premedicant, as an adjunct to balanced anesthesia, or for postoperative pain relief.