It has been reported, in the recent literature, that fifteen minutes lidocaine-MEGX (monoethylglycinexylidide) test can also be used in case of acute hepatic failure because in these conditions the test allows a rapid evaluation of the hepatic damage, uneffected by te infusion of liquid or fresh plasma which can alter conventional laboratory parameters. The Authors have demonstrated, in a experimental model, the unreliability of the lidocaine-MEGX test as measure of functional hepatic damage in the early stages of an acute liver failure. The slight decrease of the rate of the MEGX test in these animals submitted to one-stage hepatic devascularization suggests that the hepatic failure is not so early detected by this specific liver function test. Accordingly, the 15' MEGX test should not be used as isolated discriminatory measure to detect an early hepatic failure following fulminant hepatitis or an early hepatic insufficiency as a result of extensive liver resection.