For over a decade there has been concern about hepatitis related to halothane anesthesia. No dose relationship or other direct cause has ever been established, and jaundice has been found to occur after other anesthetics for surgical operations. Enflurane is a newer halogenated compound with a remarkable record of safety, yet a few cases of hepatitis are reported to be associated with its administration. We have compared effects on the liver of the two anesthetics by testing hepatic serum enzymes and sulfobromophthalein in 12 patients who received halothane and 12 who received enflurane. No significant differences between the two groups were found. Both had similar but minimal elevations of the hepatic serum enzymes and retention of sulfobromophthalein. More than half the patients had enzyme increases over normal levels but reasons for this were not obvious. Since hepatic change may take place in many postoperative patients, it is not surprising to have an occasional one develop hepatitis. The exact cause is unknown and therefore it is impossible to predict the patient who will develop the disease, regardless of the anesthetic.