Critical care nurses and physicians are familiar with the principles of patient controlled analgesia and the opioid analgesics' regimens and observations necessary for pain control in the postoperative cardiac surgical patients. The objective of the study was to compare the effects of morphine, fentanyl, meperidine, remifentanil and tramadol which were administered by patient controlled analgesia and continuous intravenous infusion combination on the various parameters. This study was designed as prospective randomised trial. Fifty patients undergone open heart surgery with sternotomy were entered equally into five randomized groups. Visual analog scale was used by researcher nurse to assess the patient' pain status. Respiratory rate, heart rate and blood gases (pO(2), pCO(2), SaO(2)), radial arterial blood pressures were measured in the first 24 hrs postoperatively. Bolus requirements were determined by physicians and side effects of the analgesics were documented. Fentanyl group showed statistically higher levels of mean pO(2) (p=0.002). Meperidine had the lowest number of bolus doses (p=0.001). There were no significant differences between the groups for pain management except higher visual analog scales on tramadol. Headache, stomachache and, palpitations were observed in our patients. Remifentanil, meperidine, fentanyl and morphine showed similar effect with each other for pain relief except tramadol.