Albumin and fibrinogen synthesis rates were measured in 15 subjects with different clinical stages of postviral cirrhosis and compared with galactose elimination capacity and aminopyrin breath test. Forty-three mg per kg body weight [2H5ring]phenylalanine with an isotopic enrichment of 10 atom% were intravenously injected. [2H5ring]phenylalanine enrichments in the plasma-free phenylalanine and the albumin and fibrinogen isolates were measured by gas chromatography-mass spectrometry. Fractional synthesis rates of albumin were normal in Child A cirrhosis (7.6 +/- 2.2%d), but were lower in both Child B (3.5 +/- 0.8%d) and C (4.5 +/- 2.8%d). Absolute rates of albumin synthesis were (103 +/- 30 mg/kg/d) in the child A group and substantially lower in the Child B (50 +/- 3 mg/kg/d) and C (36 +/- 20 mg/kg/d) group. The average fractional synthesis rate of fibrinogen was 16.7 +/- 7.5%d and the absolute synthesis rate 11.6 +/- 6.4 mg/kg/d. The values of the galactose elimination capacity and the aminopyrin breath test were below the normal range in all patients, gradually decreasing with an increase in the severity of the clinical stage of cirrhosis. Albumin synthesis rates significantly correlated with the Child scores, the galactose elimination capacity, and the aminopyrin breath test, whereas fibrinogen synthesis rates showed no such correlations.