Purpose: To evaluate the antibacterial effect of Kenger gum on mutans streptococci (in vivo) and Streptococcus mutans (in vitro) and its cytotoxic effect on the 3T3 fibroblast cell line. Materials and Methods: In vitro antibacterial activity of Kenger gum extracts against S.mutans was determined by the disk-diffusion method. The broth dilution method was used to determine the minimum inhibitory concentration (MIC). The cytotoxic effect on 3T3 fibroblast cells at different time intervals was determined using cell culture and viability assays. Clinical studies were then performed on 20 healthy adult subjects, where a sugar-free chewing gum was used as a control. To determine the MS counts, oral rinse samples were taken before chewing as well as 30 and 60 min after 15 min of chewing. Repeated-measures ANOVA was used to compare the bacteria level in the oral rinse samples between the two chewing gums. The Least Significant Difference test was used for adjustment for multiple comparisons. Results: The MIC of the acetone extract of Kenger gum was 30 μg/ml. The acetone extract of Kenger gum possessed moderate antiproliferative properties against the non-tumorigenic cell line 3T3. A statistically significant decrease was observed for both chewing gums at 30 and 60 min. The decrease continued at 60 min after chewing Kenger gum, while the values for control gum tended to approach the baseline after 60 min. Conclusion: This preliminary study showed that Kenger gum had particular and prolonged antibacterial activity against S. mutans and salivary mutans streptococci. Keywords: chewing gums, Kenger gum, mutans strepotococci