We have compared the effect of peritonsillar infiltration with tenoxicam 5 mg and placebo on postoperative pain after tonsillectomy. Fifty patients undergoing bilateral elective tonsillectomy under general anaesthesia were allocated randomly to receive peritonsillar infiltration with tenoxicam 5 mg in 8 ml of normal saline (4 ml per tonsil) or normal saline only, before tracheal extubation. Median time to first request for morphine (30 min in each group, P = 0.83), cumulative morphine requirements from 0 to 2 h after surgery (two and one doses, P = 0.50), and from 2 to 24 h after surgery (one dose in each group, P = 0.17) were similar. There were no significant differences between groups in VAS scores at rest or when drinking 100 ml of water at any time. The power of detecting a reduction in VAS scores of 20 mm was 90% at the 5% significance level.