The interaction of C. albicans with host cells has been shown to be quite complex. At least three recognition systems have been described, and, probably additional ones exist. The recognition systems are classified by the type of host cell, the growth form of the organism and the nature of the interaction at the molecular level, i.e., protein-protein or protein-oligosaccharide. It would appear that C. albicans has at least two distinct mannoprotein adhesins. One resembles a lectin in that it recognizes host cell glycosides containing fucose, and with some strains of C. albicans, N-acetylglucosamine. The second adhesin has properties similar to the integrin or transmembrane glycoproteins such as the CR3 (complement receptor 3). Still to be resolved is the characterization of the lectin-like adhesin as well as the relationship of the CR2-like activity to the CR3 of Candida. A third adhesin which is a mannan polysaccharide has been suggested as a recognition molecule in the adherence of the organism to buccal epithelial cells.