Sixty five children aged from 1-10 years who underwent herniotomy, cystolithotomy or orchidopexy received either buprenorphine 4 mug kg-1 (n=33) or morphine 50 mug kg-1 (n=32) by the caudal epidural route; each thus received 0.5 ml kg-1 body weight. General anaesthesia was given for surgery. Post-operative pain and behaviour were assessed by an independent observer at 1, 4, 8, 16 and 24 h post-operatively. Caudal morphine and buprenorphine were equally effective for post-operative analgesia in children, but buprenorphine was better because of its longer duration of action and lower incidence of side effects,