Since, functional foods have recently emerged as a novel sector of health-enhancing products, a query remains about their effectiveness on Mutans Streptococci count and its influence on caries development. This study was designed to evaluate the effect of feeding functional dairy product containing different sugar substitutes on salivary Mutans Streptococci count in experimental rats. Samples of chocolate milk were prepared.Total number of rats were 24, divided to 4 groups, 6 in each group. When rats reached the age of 21 day, all animals were infected on three consecutive days with Mutans Streptococci, rats were randomly divided, according to the type of diet, into four groups (n=6): Group 1 (Type 1 sucrose). Group2: Rats received milk with (Type 2 of sugar xylitol).Group 3 (type 3 of sugar: Group 4 (Negative control) . After every week and at the end of the 5-week experimental period, Saliva samples were collected from the oral cavity of rats. Results showed Both sugar substitutes (xylitol and stevia used in the study, don’t favor the growth of salivary Mutans Streptococci in experimental rats. Flavored chocolate milk containing stevia was more effective than that containing xylitol in reduction of Mutans Streptococci in experimental rats.