Thirty patients presented for elective valve replacement surgery were included. The patients were classified into two equal groups (15 each) according to the received opioid as a part of a balanced anesthetic technique. The first group, (morphine group), received morphine IV (0.1 mg/kg) at anesthesia induction and then (1-2 mg/h) till the end of surgery and the arrival to the ICU. The second group, (fentanyl group), received fentanyl IV (5 µg/kg) at anesthesia induction and then (1µg/kg/h) until the end of surgery and the arrival to the ICU. We concluded that, the use of morphine when compared to fentanyl as a part of a balanced anesthetic technique in valve replacement surgery after CPB, can allow better hemodynamic stability, attenuates the release of inflammatory cytokine (IL-6) and anti-inflammatory cytokine (IL-10), produce a greater reduction in adhesion molecule expression (CD 11b, CD 11c and CD 18), and reduce the incidence of postoperative hyperthermia.