The purpose of this study was to determine whether partial substitution of xylitol and soibitol for sucrose could produce changes in plaque formation, gingivitis and oral bacteriology in children. The subjects consisted of 55 volunteer schoolchildren aged 14 to 16, divided into the following groups: 1) Polyol Group (26 children), 2) No-Sweets Group (8), 3) Sucrose Group (21).During the two weeks of the study, the Polyol Group consumed chewing gum and pastilles containing xylitol and sorbitol, mainly after meals. The No-Sweets Group was instructed to consume no sweets during the study. The Sucrose Group chewed gum and ate sweets same as before the study. The variables measured were the visible plaque index (VPI), gingival bleeding index (GBI) and lactobacillus index (Dentocult®). The scores for these indices were determined at the beginning and end of the study. The results for the Polyol and No-Sweets groups were similar; both the xylitol-sorbitol mixture and abstention from sweets reduced the VPI and GBI scores substantially. In the Sucrose Group, the VPI and GBI scores remained practically unchanged. Changes in the Dentocult index were difficult to assess due to high variability, though significant differences were observed between treatment groups, polyol utilization and total abstention from sweets leading to similarly decreased scores. The results may be due to differences between the microbiological and biochemical effects of sucrose and the polyol mixture, which resulted in reductions in plaque, gingival bleeding and lactobacilli.