The exposure of either epithelial cells or pneumococci or both to 5% xylitol reduced the adherence of pneumococci. Exposure of epithelial cells or bacteria alone to xylitol did not reduce the adherence of Haemophilus influenzae, although the exposure of both cells and bacteria to xylitol reduced the adherence significantly. The adherence of Moraxella catarrhalis remained low irrespective of the exposure.