To evaluate the level of serum thyroxine-binding globulin (TBG) in various liver diseases, TBG and T4, T3, FT4 were measured by radioimmunoassay in 29 HBsAg carriers (C), 27 patients with acute hepatitis (AH), 18 patients with inactive chronic hepatitis, 70 patients with chronic active hepatitis (CAH), 31 patients with active cirrhosis (AC), 20 patients with inactive cirrhosis (IC), 38 patients with hepatocellular carcinoma (HCC), 12 patients with metastatic Ca to the liver (Met.) and in 81 normal controls. All the patients were clinically euthyroid. The TBG as well as T4 in patients with AH, CAH, AC HCC and, Met. were significantly higher than those in controls. The T3 level was significantly elevated in CAH and AC patients. The TBG level did not correlate with serum albumin or bilirubin levels, but did correlate significantly with alanine transaminase (ALT) (r = 0.54, p less than 0.01). However, the correlation was positive in chronic active hepatitis (r = 0.40, p less than 0.01) but negative in hepatocellular carcinoma (r = -0.32, p less than 0.05). The data suggested: (1) Significant TBG and T4 elevation was found in all active liver diseases and HCC. (2) In the presence of high T4 in patients with liver disease, normal FT4 excluded the diagnosis of hyperthyroidism. (3) The elevation of TBG levels in chronic hepatitis appeared to parallel the severity of hepatocytolysis, and therefore might be the result of hepatocytolysis; while the elevation of TBG in HCC might be due to increased synthesis by the malignant cells.