This prospective, randomised, double blind study compared the efficacy of pethidine as an adjuvant to bupivacaine with the efficacy of bupivacaine alone for infra-orbital nerve block in alleviating postoperative pain in children undergoing cleft lip repair. Forty paediatric patients aged between 5 and 60 months undergoing cleft lip repair were randomly allocated to two groups of 20. After tracheal intubation, group B received bilateral intra-oral, infra-orbital nerve block with 1 ml of 0.25% bupivacaine on each side and group P received 1 ml of 0.25% bupivacaine along with 0.25 mg.kg(-1) body weight pethidine. Sedation after recovery from anaesthesia was assessed using the University of Michigan Sedation Scale (UMSS) and pain was assessed postoperatively up to 36 h using the FLACC scale (Face, Legs, Activity, Cry, Consolability). The median (IQR) duration of analgesia from the time of administration of block in group B was 18 h (14.2-20) compared to 29.1 h (24-36) in group P (p = 0.001). Addition of pethidine as an adjunct to local anaesthetic significantly prolonged the duration of postoperative analgesia without any adverse effects.