Effects of sevoflurane and isoflurane anesthesia in oxygen on clinical, cardiopulmonary, hematological, and serum biochemical findings were compared in sheep breathing spontaneously undergoing minor surgical operations during short-term (60-80 min) or long-term (3-4 h) anesthesia. All sheep were premedicated with atropine sulfate (0.1 mg/kg) intramuscularly, and 10 min later, induced to anesthesia by intravenous infusion of sodium thiopental (mean 14.1 ± 3.4 S.D. mg/kg). After incubation, they were anesthetized with either isoflurane or sevoflurane in oxygen at a total gas flow rate of 1.5 l/min. The results revealed that recovery time with sevoflurane was more rapid than with isoflurane. Respiration rates, tidal volume, minute ventilation and heart rates during sevoflurane anesthesia were similar to those during isoflurane anesthesia. The degree of respiratory acidosis during sevoflurane anesthesia was also similar to that during isoflurane anesthesia. There were no significant differences between sevoflurane and isoflurane anesthesia in hematological and serum biochemical values. (C) 2000 Elsevier Science B.V.