Drug requirements, hemodynamic responses, and fluid balance were retrospectively studied in 65 male patients undergoing cardiac transplantation. Twenty patients received fentanyl-oxygen (88 +/- 7 micrograms/kg), and 45 patients received sufentanil-oxygen (20 +/- 1 micrograms/kg) as the primary anesthetic technique. The left ventricular ejection fraction averaged 15% and 18%, respectively. Hemodynamic stability was maintained during induction, bypass, and postbypass periods with both drugs. Cardiopulmonary bypass (CPB) was terminated with isoproterenol support for all patients. Additional inotropic support was required for 65% of fentanyl- and 56% of sufentanil-treated patients. Pacemaker support was required less frequently for sufentanil- than fentanyl-treated patients (P less than .01). Vasodilator therapy was required after CPB for patients receiving sufentanil despite the fact that higher-than-anticipated doses of sufentanil were administered during and after CPB. Fluid requirements were similar for both groups. It is concluded that both high-dose fentanyl and sufentanil anesthesia can provide clinically satisfactory anesthesia for cardiac transplantation.