A mannose-specific lectin, Concanavalin A, was used to pretreat Candida albicans before using the yeasts in an in vitro adherence assay. Adherence to buccal cells was inhibited but could be restored by preincubation of the lectin with a specific haptenic sugar, a-D-methylmannopyranoside, prior in the assay but not by using D-galactose, D-ribose and D-raffinose, sugars which the lectin does not recognize.