Lectin histochemistry of the normal and neoplastic human choroid plexus cells [six choroid plexus papillomas (CPPs) and three choroid plexus carcinomas (CPCs)] was performed using eight representative lectins to study the development of sugar chain structures and also to determine whether lectins were useful for a histopathological diagnosis of choroid plexus neoplasms (CPNs). The normal choroid plexus cells reacted with Ricinus communis (RCA-I). Canavalia ensiformis (Con A), Limax flavus (LFA) and Triticum vulgaris (WGA), while Arachis hypoaea (PNA) stained them only after the removal of sialic acid. Human fetal choroid plexus cells at 8 weeks gestation already showed the same lectin-binding patterns as adult ones. All CPNs were stained by RCA-I and Con A in a similar manner as the normal choroid plexus cells. Although seven CPNs were positive for LFA, two CPCs were not stained by LFA, which bound to sialic acid. Two LFA-positive CPPs were stained by PNA before the removal of sialic acid. Moreover, unlike the normal choroid plexus cells, Ulex europaeus-, Glycine maximus- and Dolichos biflorus-binding sites often appeared, and WGA-binding sites of three CPNs remained even after sialic acid removal. In conclusion, the glycosialylation in normal choroid plexus cells was completed during the early embryonic stage. The lectin-binding patterns of CPNs were heterogenous in each case. The alternation of the glycosialylation and/or acquisition of binding sites for some lectins was sometimes observed through a neoplastic transformation.