A randomized, controlled clinical trial was conducted on 72 patients undergoing elective cardiac surgery to compare patient-controlled analgesia (PCA) to nurse-titrated infusion of morphine. Pain and nausea scores were assessed at 5, 20, 32 and 44 hours after cardiopulmonary bypass. Serum cortisol estimations were performed at 24 and 48 hours, and morphine consumption was measured at 0-24 and 24-48 hours. There was no difference between pain scores (P=0.72), nausea scores (P=0.52), serum cortisol at 24 and 48 hours (P=0.32 and P=0.34), and morphine consumption at 0-24 and 24-48 hours (P=0.16 and P=0.12). There was also no difference in the time to tracheal extubation (P=0.79) and discharge from ICU (P=0.64). There was a significant association between pain and serum cortisol at 48 hours (P=0.023). This study also found a tenfold difference in the amount of morphine used (range = 11 to 108 mg), with no significant association with patient age or sex. We could find no significant benefit from the routine use of PCA in cardiac surgical patients.