Scanning electron microscopic observations of the baboon tongue demonstrating specificity of microbial distribution as related to epithelial keratinization are presented. The number of bacteria inhabiting a surface was related to the degree of keratinization. Orthokeratotic dorsal tongue surfaces were most heavily colonized by bacteria. The parakeratotic and non-keratinized surfaces were less heavily populated, with non-keratinized areas showing the fewest numbers of bacteria.