We have compared the analgesic effects of diclofenac given before operation or immediately after operation in a randomized, double-blind, double-dummy study of 40 healthy female patients undergoing laparoscopic tubal ligation. Group 1 patients received diclofenac 75 mg as a 3-ml i.m. injection 1-2 h before operation and normal saline 3 ml i.m. immediately after surgery. Group 2 patients received normal saline 3 ml i.m. before operation and diclofenac 75 mg i.m. immediately after surgery. Outcome measures were patients' perception of pain on a visual analogue scale (VAS), verbal response scale (VRS), the number of patients who required postoperative morphine, time to first postoperative morphine injection and total dose of morphine given. VAS at 30 min and at 1, 3 and 6 h after operation were, respectively (median, inter quartile range) 4.5 (2.3-6.0) vs 5.3 (2.8-7.8); 3.3 (2.3-5.0) vs 4.4 (3.0-5.8); 1.4 (0-2.3) vs 1.9 (0.8-3.0); 0.5 (0-1) vs 0.7 (0-1.3), (ns). VRS at 1 and 3 h after operation were, respectively, (median, interquartile range) 2.2 (1.5-3.0) vs 2.7 (2.0-4.0) and 0.8 (0-1.3) vs 0.9 (0-1.5) (ns). Sixteen patients in group 1 compared with 17 in group 2 required postoperative morphine. Time to first morphine administration and dose given were, respectively, (median, interquartile range) 50.6 (39-60) min vs 35.7 (20-49) min (P = 0.1) and 9.0 (5-10) mg vs 9.5 (7.5-10) (P = 0.9). We conclude that in patients presenting for laparoscopic tubal ligation, preoperative administration of diclofenac 75 mg i.m. conferred no additional analgesic benefit compared with a similar dose given after operation.