Candida albicans produces extracellular polymeric material (EP) which contains a mannoprotein adhesin. EP isolated from culture supernatants of C. albicans GDH 2346 consisted of a mixture of glycoprotein components and inhibited yeast adhesion to buccal epithelial cells by up to 60%. Partial purification of the adhesin was achieved by a two-step procedure involving chromatography of EP on concanavalin A-Sepharose and DEAE-cellulose. The purified adhesin inhibited adhesion to buccal cells 30 times more efficiently (on a weight basis) than unfractionated EP. Pretreatment of EP with heat, dithiothreitol or proteolytic enzymes either partially or completely destroyed its ability to inhibit adhesion, whereas pretreatment with sodium periodate or alpha-mannosidase had little or no effect. These results suggest that the protein portion of the mannoprotein adhesin is more important than the carbohydrate moiety in mediating yeast attachment to buccal epithelial cells.