Results are presented which support the concept that the bacterial enzyme glucosyltransferasc (GTF) plays a crucial role in sucrose induced plaque formation. GTF was shown to adlicre strongly to anionic, hydrophobic and polysaccharide solid materials, and to be able to produce glucans in the adsorbed state. It appears conceivable that GTF adsorb to teeth and produce glucans. Glucan chains on the surface of the bacteria and glucans on the tooth surfaces interact (pack) and form a strong binding mechanism. The rigid al,3 linked glucans produced by Streptococcus mutans arc particularly suited for interaction of this kind. This mechanism could account for sucrose-induced binding of bacteria to enamel, pellicle covered enamel and preformed plaque. S. mutans would adhere particularly strongly to tooth surfaces in the presence of sucrose, according to thi.s model.