The authors compared the incidence of respiratory complications and arterial hemoglobin desaturation during emergence from anesthesia in children whose tracheas were extubated while they were anesthetized or after they were awake and to whom halothane or isoflurane had been administered. One hundred children 1-4 yr of age undergoing minor urologic surgery were studied. After a standard induction technique, patients were randomized to receive either isoflurane or halothane. In 50 patients tracheal extubation was performed while they were breathing 2 MAC of either halothane or isoflurane in 100% oxygen. The remaining 50 patients received 2 MAC (volatile agent plus nitrous oxide) during the operation, but tracheal extubation was delayed until they were awake. A blinded observer recorded the incidence of respiratory complications and continuously measured hemoglobin saturation for 15 min after extubation. When tracheal extubation occurred in deeply anesthetized patients, no differences were found between the two volatile agents. When tracheal extubation of awake patients was performed, the use of isoflurane was associated with more episodes of coughing and airway obstruction than was halothane (P less than 0.05). Awake tracheal extubation following either agent was associated with significantly more episodes of hemoglobin desaturation than was tracheal extubation while anesthetized.