A prospective, double-blind, randomized, controlled study was undertaken to compare the perioperative analgesic and recovery characteristics of equipotent doses of tramadol, pethidine and nalbuphine (3.0 mg kg-1, 1.5 mg kg-1 and 0.3 mg kg-1 respectively) with placebo (saline 0.02 ml kg-1) given at induction of anaesthesia in 152 ASA 1 children and young adults undergoing tonsillo-adenoidectomy. Premedication (temazepam and diclofenac), induction and maintenance of anaesthesia (thiopentone, atracurium, nitrous oxide and isoflurane), with controlled ventilation, were standardized. Variables monitored were heart rate (HR) and systolic arterial pressure (SAP) during surgery, time to recovery of spontaneous respiration at the termination of anaesthesia and restlessness, time to awakening, sedation and emesis in the recovery unit. Increases in HR or SAP > 33% of baseline during surgery were treated with esmolol 2.0 mg kg-1 intravenously (i.v.) and restlessness during recovery was treated with the same opioid i.v. given with an aesthesia, or pethidine i.v. in the placebo group. With placebo, there was a high requirement for esmolol during surgery and for pethidine in the recovery ward. Tramadol did not reduce the rate of intra-operative treatment with esmolol, but reduced the tramadol requirement during recovery (P < 0.05). Pethidine and nalbuphine reduced the intra-operative esmolol requirement more significantly (P < 0.025 and P < 0.005 respectively) and the need for treatment during recovery with opioids (P < 0.005 each). The time to recovery of spontaneous respiration at the end of anaesthesia was only delayed by pethidine. Other recovery variables were similar, except that restlessness-pain scores were reduced by tramadol (P < 0.02), pethidine (P < 0.005) and nalbuphine (P < 0.005). These results suggest that pethidine 1.5 mg kg-1 and nalbuphine 0.3 mg kg-1 given with induction of anaesthesia provide better analgesia during and after tonsillo-adenoidectomy than does tramadol 3.0 mg kg-1. The delay to recovery of spontaneous respiration with pethidine suggests a greater safety profile of nalbuphine and tramadol.