Certain environmental, physical, and biochemical aspects of Candida albicans adherence to human vaginal epithelial cells were characterized by using an in vitro radiometric adherence assay. Blastospores harvested from cultures grown at 25 degrees C adhered to vaginal epithelial cells in significantly greater numbers than did blastospores isolated from cultures grown at 37 degrees C. C. albicans viability was not essential for adherence, but severe methods used to kill the blastospores did reduce their attachment. The addition of sodium chloride, divalent cations, sugars, mannan, or mannoprotein to the assay had no effect on attachment. Pretreatment of the blastospores with detergents, salts, urea, glycosidases, lipase, or pepsin did not affect adherence, but treatment with reducing agents or five proteolytic enzymes did render C. albicans nonadherent. Cell wall fragments prepared from C. albicans, but not from Candida krusei, adhered to vaginal epithelial cells. Loss of adherence after the cell walls were treated with alpha-mannosidase or papain suggests that cell wall mannoprotein is an essential component of the C. albicans adhesin.