alpha 1-Acid glycoprotein, an acute phase reactant synthesised by the liver, has been reported to be increased in neoplastic conditions and reduced in chronic liver disease. We measured serum alpha 1-acid glycoprotein by a nephelometric method in 186 subjects (112 males, 74 females): 55 had mild chronic liver disease (chronic hepatitis and steatofibrosis), 45 cirrhosis, 38 hepatocellular carcinoma, 15 extra-hepatic malignant disease; 33 healthy subjects were used as controls. Analysis of variance demonstrated a significant variability among groups (F = 17.08, P = 0.0000). Higher concentrations of alpha 1-acid glycoprotein were detected in malignant extra-hepatic disease than in all other groups (P < 0.01); concentrations of alpha 1-acid glycoprotein were higher in hepatocellular carcinoma than in cirrhosis (P < 0.01). Multiple regression analysis by groups (dependent variable = alpha 1-acid glycoprotein; group 1 = mild chronic liver disease + cirrhosis; group 2 = hepatocellular carcinoma) showed a significant correlation for both group 1 (r = 0.6264, F = 8.005, P = 0.0000) and group 2 (r = 0.8947, F = 13.643, P = 0.0000). The significant standardised regression coefficients were: cholinesterase, C-reactive protein, gamma-glutamyltransferase and iron (negative) for regression upon group 1; C-reactive protein, alpha 1-antiproteinase, gamma-glutamyltransferase, iron (negative) for regression upon group 2. A difference between the 2 regression equation coefficients was detected (F = 5.209, P = 0.0002).(ABSTRACT TRUNCATED AT 250 WORDS)