Xylitol-sweetened chewing gum has cariostatic properties, but is not suitable for all patients. This study evaluated the effect of xylitol rinse on mutans streptococci (MS) levels in the mouth. One hundred and five subjects with high salivary MS levels were randomly assigned to one of three groups. Subjects in the positive control group (N = 35) chewed two xylitol gum pellets for at least 5 minutes three times daily (xylitol dose: 4.3g/day). The experimental group (N = 36) rinsed with 20 mL of an aqueous solution of xylitol twice daily for 60 seconds (dose: 4.4 g/day). The negative control group (N = 34) used neither product. No attempt was made to change the subjects' diet. Mean MS levels at baseline were 5.6 (0.1) in positive control, 5.4 (0.1) in experimental, and 5.5 (0.1) in negative control groups. After 3 months, MS levels were 4.4 (0.2), 4.4 (0.2), and 4.9 (0.2), respectively. Differences between groups were not significant by ANOVA (p = .2); however, MS levels tended to be lower in the experimental and positive control groups. Xylitol rinse and chewing gum caused a similar but statistically insignificant reduction in MS levels in the mouth.