The effect of 2–month usage of saliva–stimulating pastils containing either erythritol or xylitol was studied in a cohort of 30 subjects assigned to the respective polyol groups (n = 15). The daily consumption level of both polyols was 5.2 g, used in 5 daily chewing episodes. The mean weight of total plaque mass (collectable during a standard period of 3 min from all available tooth surfaces) was reduced significantly in the xylitol–group, while no such effect was observed in the erythritol–group. This reduction in plaque mass was accompanied by a significant reduction in the turbidity readings (A660) of aqueous plaque suspensions; no such effect was observed in the erythritol–group. However, plaque protein levels did not differ between baseline and endpoint in either polyol group. The plaque and salivary levels of Streptococcus mutans and plaque levels of total streptococci were reduced significantly in the xylitol–group, while no such effect was detected in the erythritol–group. However, either polyol regimen had no effect on plaque levels of S. sobrinus. The results suggest that systematic use of xylitol–containing saliva stimulants may be more effective in controlling some oral–hygiene–related and caries–associated parameters than similar use of erythritol–containing products. The results also speak for a special relationship between xylitol and S. mutans. However, owing to the great potential of erythritol as a caries–reducing agent – based on the tetritol nature of erythritol – the present laboratory results should be considered preliminary and subject to verifying clinical studies.