The maturation process of basal cells in craniopharyngiomas was studied using a panel of lectins, and antibodies against cytokeratin 13 and bcl-2 protein, using oral mucosa for comparison. Seven lectins were employed: peanut (Arachis hypogaea) agglutinin, Dolichos biflorus agglutinin (DBA), Ulex europaeus agglutinin-I (UEA-I), soybean agglutinin, Ricinus communis agglutinin-I, succinyl wheat germ agglutinin, and Pisum sativum agglutinin. DBA and cytokeratin 13 stainings of the suprabasal cells in craniopharyngiomas were comparable to those of the oral mucosa, but not to those of the skin. Staining patterns of the basal cells in the oral mucosa and craniopharyngiomas were generally similar, but UEA-I binding and bcl-2 protein expression in suprabasal cells differed. The difference appeared to be due to a disturbance in the differentiation of the basal cells, because only a small fraction of the basal cells followed a normal maturation process in craniopharyngiomas in comparison to the oral mucosa. The expression of bcl-2 protein may be involved in the pathogenesis of craniopharyngiomas.