The strains of group A streptococci associated with pyoderma appear to be distinct from those associated with acute pharyngitis. It has been suggested that the capacity of a given microorganism to colonize a particular epithelial surface is proportional to the ability of the organism to adhere to that surface. Group A streptococci isolated from skin adhere in greater numbers to human skin epithelial cells than to cells obtained from buccal mucosa, whereas streptococci isolated from a throat tend to adhere in greater numbers to buccal epithelial cells than to skin epithelial cells in vitro. M protein-producing strains of group A streptococci did not adhere in significantly greater numbers than M-negative strains. Lipoteichoic acid inhibited binding of streptococci to skin epithelial cells as well as was previously shown for oral epithelial cells. The results suggest that lipoteichoic acid is more centrally involved than M protein in binding streptococci to skin and mucosal surfaces.