Histochemical evaluation of lectins was performed to examine the carbohydrate residues of oval cells induced by administration of alpha-naphthylisothiocyanate (ANIT), 2-acetylaminofluorene (2-AAF) and 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) in comparison with those of normal bile ducts and proliferated bile ductules induced by bile duct ligation. The normal bile ducts showed intense binding of Ricinus communis agglutinin, concanavalin A and wheat germ agglutinin, and weak binding of Ulex europaeus agglutinin I (UEA I). A few cells in the portal bile ducts showed binding of peanut agglutinin (PNA). Two different binding patterns were observed in oval cells and proliferated bile ductules. One group showed increased binding of PNA, while the other showed intense binding of UEA I. In both groups, binding of other lectins was similar to those of the normal bile duct. The first group included oval cells induced by 2-AAF and 3'-Me-DAB, and the second included both oval cells induced by ANIT and proliferated bile ductules induced by ligation. These results suggest that oval cells and proliferated bile ductules have their own specific carbohydrate residues and that oval cells induced by the carcinogens might be a cell population different from those induced by non-carcinogens and proliferated bile ductules by ligation.