Lidocaine is converted to its primary metabolic product monoethylglycinexylodide (MEGX) via cytochrome P-4503A4 within the liver. A steady-state concentration of MEGX appears in serum within 15 min following the intravenous administration of lidocaine. The present article reviews some of the data suggesting that this MEGX value can be utilized to assess hepatic function. MEGX production declines stepwise with the severity of chronic hepatitis. In patients with cirrhosis, MEGX declines further with worsening Child class. Nearly all persons with MEGX of < 20 ng/ml had cirrhosis confirmed upon histologic evaluation. Severe life-threatening complications of cirrhosis were observed only in patients with MEGX production below 20 ng/ml. One-year survival for patients with an MEGX value of < 10 ng/ml was only 50%. In contrast, 1-year survival for patients with MEGX of > 10 ng/ml was approximately 80%. These data suggest that MEGX could be utilized as an accurate test of hepatic function and to predict morbidity and mortality related to complications of chronic liver disease. However, this test does have several limitations. There is wide interpatient variability between MEGX and hepatic histology, which severely impairs the ability of this test to accurately predict hepatic histology. In addition, MEGX is affected by gender and several medications. However, since MEGX does decline stepwise with advancing histology in any given patient, the available data suggest that serial monitoring of MEGX could be utilized to track hepatic metabolic capacity in patients with chronic hepatitis and cirrhosis.