To evaluate glycine conjugation of para-aminobenzoic acid (PABA) to the hippurated metabolites, para-aminohippuric acid (PAHA), and para-acetamidohippuric acid (PAAHA) as a quantitative liver function test in patients with liver disease. Serum concentrations of PABA and metabolites were measured by high pressure liquid chromatography in 24 controls and 50 patients with hepatobiliary disease. Hippurate formation was significantly decreased in all patient groups with chronic liver disease versus controls. The hippurate ratio (% hippurated metabolites formed) correlated with severity of disease, serum albumin, and factor VII concentrations. PAHA concentration was a better prognostic indicator than factor VII concentrations in patients with acute liver disease; concentrations of zero correctly predicted a poor outcome in patients with fulminant liver failure. Glycine conjugation of PABA may be useful as a quantitative liver function test in patients with hepatobiliary disease and as a prognostic index in patients with fulminant liver failure.