Boronate affinity chromatography of gamma-glutamyltransferase in patients with hepatocellular carcinoma. We analyzed the serum gamma-glutamyltransferase (gamma-GT) by boronate affinity chromatography to ascertain the presence or absence of any changes in the binding properties of gamma-GT toward boronate gels in patients with hepatocellular carcinoma and liver cirrhosis, and in normal controls. The mean gamma-GT activity ratio of the bound (peak 2) and nonbound (peak 1) fraction in patients with hepatocellular carcinoma was significantly higher than that in patients with liver cirrhosis or in normal controls. Thus, the gamma-GT, which has adjacent cis-hydroxyl groups in its carbohydrate moieties, was found to increase in the serum of patients with hepatocellular carcinoma. The positivity rate was examined in patients with hepatocellular carcinoma and liver cirrhosis, using a cut-off level for the peak 2:peak 1 ratio of 1.05 (mean + 2 SD of liver cirrhosis). Nineteen (42.2%) patients with hepatocellular carcinoma had a ratio of peak 2:peak 1 higher than 1.05. Nine of the 19 patients who had serum alpha-fetoprotein levels below 100 ng/ml had an elevated peak 2:peak 1 ratio. In total, 77.8% of the occurrence of hepatocellular carcinoma could be detected by a combination of these two markers. Three patients who had developed hepatocellular carcinoma during the course of cirrhosis but remained negative for alpha-fetoprotein throughout the course developed higher levels of peak 2:peak 1 ratio when hepatocellular carcinoma occurred. These results indicate that the two markers, the peak 2:peak 1 ratio of serum gamma-GT activity and serum alpha-fetoprotein level, may be considered to serve as complementary markers for the diagnosis of hepatocellular carcinoma. 