The purpose of this study was to determine partition coefficients for a new, rapid-acting inhaled anesthetic, sevoflurane. Blood samples were taken from 19 ASA physical status I-III patients ranging in age from 21 to 77 yr who were scheduled for elective surgery. At 37 degrees C, we found a blood/gas partition coefficient of 0.686 +/- 0.047 (mean +/- SD), a saline/gas partition coefficient of 0.370 +/- 0.016; and an oil/gas partition coefficient of 47.2 +/- 2.7. These values are consistent with the clinical observation that sevoflurane is a potent inhaled anesthetic that produces a rapid induction of and recovery from anesthesia.