This prospective, randomized study compared postoperative pain scores, morphine consumption and length of stay in 95 adults who underwent elective lumbar spine surgery via a posterior incision. Immediately prior to closure the wound was irrigated with triamcinolone 40, 20 or 0 mg. Visual analogue scale pain scores at 24 h after surgery were median 12 (interquartile range 3-24), 15 (6-34) and 33 (20-59) mm for patients receiving triamcinolone 40, 20 mg or no steroid, respectively (P < 0.0005, Kruskal-Wallis test). Total morphine usage after 24 h was 26 (21-39), 27 (17-43) and 43 (27-73) mg for the same groups (P < 0.001, Kruskal-Wallis test). The proportion of patients discharged from hospital on the first day after surgery was 83.9, 77.4 and 54.8% for patients receiving triamcinolone 40, 20 mg and no steroid, respectively (P < 0.028, chi-squared test). Extra-dural triamcinolone reduces pain after lumbar spine surgery and reduces time to discharge from hospital.