Batch culture techniques were used to study the effect of sorbitol and xylitol on the aggregation, adhesion and solubility of the polysaccharides produced by Streptococcus mutans in the presence of 3% sucrose. Both polyols increased the production of soluble polysaccharides: control < xylitol < sorbitol. The presence of sorbitol increased also the amount of insoluble carbohydrates associated with the cell mass, whereas xylitol decreased the amount of these polysaccharides compared to the control. The highest amount of total polysaccharides was produced in the presence of sorbitol: sorbitol > xylitol ≃ control. The ratio of soluble polysaccharides to insoluble polysaccharides was higher for cells grown in the presence of xylitol compared with those grown in the presence of sorbitol. When cell-cell aggregation of the bacteria was studied, the lowest degree of aggregation was observed in the medium supplemented with 6% xylitol. The adhesivity of the cells to glass surfaces was reduced in the presence of the polyols in the basal medium as follows: control ≥ sorbitol > xylitol. Thus, in cell-cell and cell-glass interactions of S. mutans, the ratio of easily soluble to insoluble polysaccharides seems to play a more important role than the absolute amounts of soluble, insoluble or total polysaccharides per se.