We have studied the effect of continuous extradural analgesia with bupivacaine and morphine, initiated before or after colonic surgery, in a double-blind, randomized study. Thirty-two patients were allocated randomly to receive an identical extradural block initiated 40 min before surgical incision (n = 16) or at closure of the surgical wound (n = 16). The extradural regimen consisted of a bolus of 7 ml of plain bupivacaine 7.5 mg ml-1 plus morphine 2 mg and continuous extradural infusion of a mixture of bupivacaine 7.5 mg ml-1 plus morphine 0.05 mg ml-1, 4 ml h-1 for 2 h, followed by a continuous extradural infusion of a mixture of bupivacaine 2.5 mg ml-1 plus morphine 0.05 mg ml-1, 4 ml h-1, continued for 72 h after operation. In addition, all patients received similar general anaesthesia. There was no significant difference in request for additional morphine and no significant differences between the groups in pain scores (visual analogue scale or verbal) during rest or ambulation at any time of measurement. These results do not suggest that timing of analgesia with a conventional extradural regimen is of major clinical importance in patients undergoing colonic surgery.