We compared the effects of rectally administered diclofenac (12.5 mg) with paracetamol (125 mg) on pre- and postoperative behaviour and the need for supplementary analgesia in 44 children scheduled for adenoidectomy (with or without myringotomy). The study drugs were given in combination with diazepam (0.5 mg.kg-1) about 20 min before the children were taken to the operating theatre. On arrival there, the children who had received diclofenac were significantly quieter (< 0.05), easier to handle (p < 0.01) and cried less (p < 0.05) than those in the paracetamol group. During recovery, children in the diclofenac group needed fewer supplementary doses of intravenous pethidine than those receiving paracetamol (p < 0.001). There were no obvious differences between the groups in intra-operative bleeding (as estimated by the surgeon), or in measured blood loss. No postoperative complications became evident. The pre-operative rectal administration of diclofenac for pain relief after adenotomy is safe and effective.