Chest tube removal in the postcardiac surgical patients is a painful and distressful event. Fentanyl and sufentanil have not been used for pain control during chest tube removal in the postoperative period. We compared efficacy offentanyl and sufentanil in controlling pain due to chest tube removal. One hundred and forty one adult patients undergoing cardiac surgery were recruited in a prospective, randomized, double blind, placebo controlled study. Patients were randomized to receive either 2 microg/Kg fentanyl IV or 0.2 microg/Kg sufentanil IV or 2 ml isotonic normal saline, 10 min before removing chest tubes. Pain intensity was assessed by measuring visual analog scale pain score 10 minutes before removing chest tubes and 5 min and 20 min after removing chest tubes. Level of sedation, heart rate, arterial pressure, oxygen saturation, and respiratory rate were recorded by a blinded observer at the same time intervals. Mean pain intensity scores 10 minutes before removal of chest tubes infentanyl, sufentanil and control groups were 23.88+/-5.2, 25.10+/-5.39 and 23.64+/-6.10 respectively. The pain scores 5 minutes after chest tube removal were reduced to 20.11+/-6.9 (p<0.05) in the fentanyl group and 13.60+/-6.60 (p<0.05) in the sufentanil group, whereas in control group pain scores increased to 27.97+/-8.39 (p<O.05). The pain scores in sufentanil group were significantly lower compared with fentanyl or control group. Sedation scores remained low in all groups and patients remained alert and none of the patients showed any adverse effects of opioids. Heart rate, arterial pressure and respiratory rate had least variations in sufentanil group than fentanyl or control group.