This chapter deals with cell surface proteins in two Candida species, C. albicans and C. glabrata, and in their nonpathogenic relative Saccharomyces cerevisiae, specifically focusing on the diversity and function of proteins implicated in adherence of the yeasts to each other or to other surfaces, including host cells. The most extensively studied family of adhesins in any Candida species is the one corresponding to the C. albicans ALS gene family, which includes eight family members. Two adhesins in family IV have similarity to the protein corresponding to DAN1 in S. cerevisiae, another subtelomeric adhesin whose expression is regulated by oxygen availability in the environment. Mass spectrometry was identify covalently linked cell wall proteins (CWPs), including adhesins, on the surface of C. glabrata. In total, five adhesins were detected: Epa6 and four uncharacterized proteins that were subsequently named Awp1 to -4 (adhesin-like wall protein). The FLO genes play essential roles during flocculation, a process by which yeast cells bind to the mannose residues on the surface of neighboring cells, forming clusters of cells called flocs, and sediment. CWPs are key to the interaction of fungi with the environment, and not surprisingly, changes within the CWP repertoire accompany the evolutionary adaptation to a particular niche. The relatively limited repertoire of FLO genes in S. cerevisiae primarily serves to mediate yeast-yeast interactions that adapt it to growth in communities/biofilms as well as to respond to nutritional cues.