Twenty-six patients undergoing abdominal hysterectomy (ASA 1-2) were entered into a double-blind randomised trial to determine: (a) whether diclofenac given intravenously could influence the effective duration of a continuous epidural infusion of bupivacaine 0.5%, and (b) whether morphine given intravenously altered the height of the regressing block. A block to T4 was established pre-operatively and a continuous infusion of 0.5% bupivacaine 8 ml.h-1 ran for 14 h. Thirteen patients received 50 mg diclofenac intramuscularly before surgery repeated at 4 and 10 h later and 13 patients received saline intramuscularly. The height of blockade and pain scores were measured hourly. Effective block duration was defined as regression to T10 or lower and/or a pain score of 2 or more. At this point 10 mg of morphine was given intravenously and the height of the block reassessed. Duration of blockade was not significantly prolonged (p > 0.05), but pain scores were significantly reduced with diclofenac (p < 0.01). Morphine did not alter blockade height. It is concluded that epidural bupivacaine and diclofenac act additively on postoperative pain.