In 30 patients undergoing cardiac surgery, anaesthesia was induced with alfentaml 125 μg kg−1 and maintained with an infusion of alfentanil 0.5 mg kg−1 h−1 until the start of cardiopulmonary bypass, and alfentanil 0 25mg kg−1h−1 thereafter until the end of surgery. Pancuronium was given and the lungs ventilated with air in oxygen. In the majority of patients, there were no tignifiranr changes in cardiovascular measurements throughout the study, although two received sodium nitroprusside for the control of hypertension, and in one patient hypertension was so severe that the method of anaesthesia was abandoned. Transient hypotension occurred on induction in one patient. Twenty-six patients required alfentanil supplementation before bypass. These results indicate that anaesthesia with an alfentanil infusion provides satisfactory cardiovascular stability for cardiac surgery.