The authors evaluated the return of sensory, motor, and sympathetic nervous system function following caudal block in children. Twenty children, ASA PS I, aged 5 +/- 4 yr (mean +/- SD), weighing 22 +/- 9 kg, scheduled for lower abdominal and urologic surgical procedures were studied. Anaesthesia was induced and maintained by halothane, N2O and oxygen. A caudal block was performed with 1 ml/kg of 0.25% bupivacaine. Analgesia assessed by Broadman's score was efficient in 18 out of the 20 children during the first 4 hours after the block. Upper level of cutaneous analgesia was T10 +/- 2 after the block. Two hours after the caudal injection an incomplete motor blockade was found in 14 of 20 children, and at 4 hours no block was found in any child. Heart rate was significantly increased in the upright position (122 +/- 12 to 131 +/- 26 bpm at 2 hours, and 110 +/- 21 to 118 +/- 28 bpm at 4 hours), whereas arterial blood pressure was unchanged in the upright position.