This study involves 60 patients below the age of 14 years who were subjected to short duration surgical procedures under inhalation anesthesia with halothane and isoflurane at equivalent CAM in 50% protoxide. The objectives of the study were: a) to establish which of the two inhalational agents produced the more rapid anesthetic induction; b) to determine which exerted the more marked potentiation of the neuromuscular blockade induced by succinylcholine, and c) to compare the anesthetic quality during the induction and recovery periods of both halogenated agents. Induction was more rapid after halothane (mean induction time of 2.91 +/- 0.97 min) than after isoflurane (mean induction time of 6.24 +/- 2.88 min; p less than 0.001). Potentiation of succinylcholine induced neuromuscular blockade was greater after isoflurane than after halothane: the mean time of apnea was 4.56 +/- 1.82 min for isoflurane and 3.41 +/- 1.63 min for halothane (p less than 0.05). Undesirable effects were larger in patients treated with isoflurane than in patients anesthetized with halothane (mean score: 12.60 +/- 3.53 points vs 14.41 +/- 2.33 points; p less than 0.001). The analysis of anesthetic quality during the recovery period gave a mean punctuation of 16.62 +/- 2.21 to patients treated with halothane, whereas patients anesthetized with isoflurane showed a lower score of 14.25 +/- 1.99 points (p less than 0.001). The higher scores corresponded to the most well tolerated anesthetic induction and recovery. The highest attainable score in this study was 18.