BACKGROUND: To determine the efficacy and safety of intravenous postoperative morphine titration in the elderly compared with younger patients. METHODS: In the post-anaesthesia care unit, patients complaining of pain received morphine until adequate pain relief. Intravenous morphine was titrated as 3 mg boluses in young (age 65 yr) and 2 mg in elderly patients (>65 yr) every 5 min. RESULTS: We studied 350 young and 68 elderly patients. There were no significant differences between the two age groups for pain intensity at the onset of titration (numerical rating scale, 7.4 +/- 1.7 in young vs. 7.5 +/- 1.7 in elderly patients), area under the curve of numerical rating scale vs. morphine boluses (97.7 +/- 59.6 vs. 98.2 +/- 62), number of boluses required to obtain pain relief (3 +/- 1.3 vs. 3 +/- 1.3), percentage of titration failures (10% vs. 9%) and incidence of excessive sedation (18% vs. 21%). Renal clearance was significantly reduced in elderly compared with young patients (55 +/- 21 vs. 85 +/- 15 mL min(-1); P < 0.0001). CONCLUSION: Using lower bolus doses, pain relief in the immediate postoperative period with morphine was as efficacious and safe in elderly patients as in younger patients. The decrease in renal clearance of morphine in the elderly justifies the reduction of intravenous morphine boluses for the treatment of postoperative pain.