Purified alpha-fetoprotein (AFP), fucosylated AFP mixtures, and 40 sera from patients with AFP-producing hepatocellular carcinoma were analysed by monoclonal enzyme immunoassay (EIA) to distinguish fucosylated and nonfucosylated AFP molecular variants. FUC-AFP-25 was discriminated from FUC-AFP-75 by the EIA using monoclonal antibody 18H4 in the range of total AFP concentrations from 100 to 800 ng/mL. In addition, sera from 40 patients with hepatocellular carcinoma, with AFP concentrations from 100 to 1270 ng/mL and with fucosylated AFP from 0 to 100% by conventional cross immuno-affinoelectrophoresis, were also analysed by the present EIA. A statistically significant correlation was obtained between the data from the present EIA and from the conventional crossed immuno-affinoelectrophoresis in the range of fucosylated AFP more than 20% and the serum concentration of AFP more than 100 ng/mL. These results indicate that the present EIA is useful for clinical detection of hepatocellular carcinoma during the follow-up of patients with chronic liver diseases.