It has been suggested that high plasma levels of alfentanil are required in order to control hemodynamic responses to noxious stimuli in patients undergoing myocardial revascularization. The present study was designed to determine the hemodynamic profile in 10 patients and the time course of alfentanil plasma concentrations and pharmacokinetics (7 patients) during and following coronary artery surgery using alfentanil administration based on an overdosage principle. Premedication consisted of lorazepam, 0.07 mg/kg, given 2 hours before surgery. Ten milligrams of alfentanil was given over 5 minutes for anesthesia induction, followed by an infusion of 60 mg/h until sternotomy and 30 mg/h up to skin closure. Additional 5-mg boluses were given prior to noxious intraoperative events. Hemodynamic measurements were performed prior to cardiopulmonary bypass. Blood was sampled simultaneously prebypass and then during the postbypass period for determination of alfentanil plasma levels. The very high alfentanil plasma concentrations achieved provided satisfactory intraoperative conditions in most, but not all, patients. Recovery time was short, despite the large amounts of narcotic used. It is concluded that very high doses of alfentanil associated with lorazepam premedication resulted in hemodynamic stability and markedly elevated narcotic plasma concentrations in most patients. Such plasma levels seem to provide satisfactory anesthetic conditions.