Serum or ascites alpha-fetoprotein (AFP) from patients with hepatocellular carcinoma and from a cord blood were analyzed by affinity electrophoresis with two lectins mixed in agarose gel in a combination of concanavalin A (Con A) and Lens culinaris agglutinin A (LCA-A) or of erythroagglutinating phytohemagglutinin (E-PHA) and Allomyrina dichotoma lectin (allo A). Con A- and LCA-A-reactive AFP-C2-L3 was not further retarded by mixing with either of the other lectin. It showed a mobility identical with that of AFP-C2 or AFP-L3. E-PHA- and allo A-reactive AFP-P4-A3 showed similar results. It migrated with intermediate mobilities of AFP-P4 and AFP-A3 depending on the concentrations of the two lectins mixed in the gel. The results indicate that the two mixed lectins compete with each other for the topologically different lectin-binding sites on the oligosaccharide of AFP molecule.