We performed a double-blind controlled trial to compare the analgesic effect of two nonsteroidal anti-inflammatory drugs. We compared rectal diclofenac 100 mg given 1 h before induction of anaesthesia with intravenous ketorolac 10 mg given immediately before anaesthesia in 40 patients undergoing arthroscopy of the knee as day cases. A visual analogue scale was used to assess pain prior to discharge. Pain, analgesic consumption, sleep disturbance and restriction of activities were recorded by telephone enquiry 24 h after surgery. There was no difference in the pain parameters, sleep disturbance, or restriction of activity between groups. We suggest that ketorolac 10 mg intravenously and diclofenac 100 mg rectally provide comparable postoperative analgesia in the first 24 h after arthroscopy of the knee.