The aim of the present study was to further investigate the plaque-reducing effect of a xylitol-containing chewing gum. Ninety-six dental students were divided randomly into three groups: a sucrose group (n = 32), a xylitol group (n = 36) and a control group (n = 28), using a sucrose-containing chewing gum, a xylitol-containing chewing gum, or no chewing gum, respectively, during a three-day experimental plaque growth period with restricted oral hygiene. The fresh weight of plaque collected in the xylitol group was 40 % lower than in the sucrose group, along with a significantly lower mean plaque index. The use of the xylitol chewing gum induced low invertase-like activity in plaque extra-cellular phase together with low carbohydrate content. These results concur to indicate advantageous effects through the use of a xylitol-containing chewing gum.