We have compared the postoperative morphine requirements and analgesic efficacy of four doses of i.m. ketorolac 30 mg administered 6-hourly with placebo in a double-blind study of patients undergoing major or minor orthopaedic surgery. During the 24-h postoperative study period which began at the end of surgery, patients were prescribed i.m. morphine 10 mg as required 2-hourly and assessments were made of pain at 4 and 24 h. After major surgery, the median morphine consumption over 24 h was 10 mg in patients who received ketorolac, compared with 30 mg in those who received placebo (P = 0.008). Visual analogue pain scores and verbal pain assessments were better than placebo at 4 h (P = 0.028 and P = 0.008, respectively), but were not statistically different between the groups at 24 h. Overall assessment of pain was similar in both groups who had undergone major surgery. In the minor surgery groups, median morphine consumption was 0 mg in patients who received ketorolac, compared with 10 mg in those given placebo (ns). Visual analogue pain scores at 24 h after surgery were significantly less in patients who had received ketorolac compared with placebo (P = 0.046) and the overall assessment of pain relief was better in the ketorolac group (P = 0.0007). Mandatory administration of ketorolac appeared to be of benefit in both major and minor orthopaedic surgery, although the principal effects were reduction in requirement for supplementary morphine for major surgery and better overall analgesia for minor surgery.