Because of its nonpungent odor and low blood-gas solubility coefficient, sevoflurane might be an ideal drug for single-breath inhaled induction of anesthesia. Fifty ASA grade I-III ambulatory surgical patients (18-76 yr old) received a single-breath induction with either 5.0% sevoflurane or 5.0% isoflurane (randomized) in a 1:1 N2O/O2 mixture. Anesthesia was maintained with the same anesthetic in 70% N2O until the end of surgery, when anesthetics were abruptly discontinued. Induction times (loss of eyelash reflex) were similar for sevoflurane (75 +/- 3 s, mean +/- se) and isoflurane (67 +/- 4 s, P = not significant). Sevoflurane patients were less likely to have complications during induction (P < 0.005); coughing occurred more frequently with isoflurane (P < 0.001). During induction, heart rate increased with both sevoflurane (from 73 +/- 3 to 90 +/- 4 bpm, P < 0.05) and isoflurane (from 70 +/- 2 to 92 +/- 2 bpm, P < 0.05); the increase with isoflurane was greater than that with sevoflurane. Times to eye opening for sevoflurane (8.1 1 +/- 1.0 min) did not differ significantly from those for isoflurane (10.6 +/- 1.3 min). Patients opened their eyes at lower end-tidal minimum alveolar anesthetic concentration (MAC)-fractions of sevoflurane (0.12 +/- 0.01 MAC) than isoflurane (0.15 +/- 0.01 MAC, P < 0.01). During recovery, patients who received sevoflurane felt less clumsy (P < 0.001) and less confused (P < 0.005) but had higher pain scores (P < 0.005) than those who received isoflurane. Sevoflurane is more suitable than isoflurane for single-breath induction, because it produces a smoother induction with a lower incidence of complications and better patient acceptance.