Ikuo Yamashina determined the two notable structures of N-glycans, N-acetylglucosaminylasparagine and β-mannosidic linkages, which are generally present in sugar–amino acid and innermost mannose residue of the N-glycans, respectively. He detected mucins with unusual O-glycans and proteoheparan sulphate in the plasma membranes of AH66 ascites hepatoma cells. Unusual O-glycans were identified as tumour-associated carbohydrate antigens after the development of monoclonal antibodies against these O-glycans. Epitopic structures of some antigens were determined to comprise clusters of short O-glycans aligned on the core peptide, which may be not only antigenic but also functional in relation to tumour behaviour. With respect to proteoheparan sulphate, this finding led to study on membrane-bound proteoglycans.