BACKGROUND: Xylitol administered regularly 5 times a day after each meal is successful in preventing acute otitis media (AOM) in children, but if given only during respiratory infections it is ineffective against AOM. To find a more convenient dosing regimen, we tested whether xylitol administered 3 times a day reduces the occurrence of AOM. METHODS: In this 3-month randomized, double-blind trial, 663 healthy day care children were randomized to receive either a control product (n = 331) or xylitol (n = 332). Xylitol was given in chewing gum or in a mixture 3 times a day, the daily dose being 0.5 g in the control group and 9.6 g in the xylitol group. The occurrence of the first AOM diagnosed during any period of respiratory symptoms during the follow-up was the main outcome measure. RESULTS: At least one AOM episode was diagnosed in 98 of the 331 children who received control products (30%) and in 94 of the 332 who received xylitol products (28%). A total of 142 episodes of AOM were diagnosed in the control group compared with 156 in the xylitol group. The differences were not statistically significant. CONCLUSIONS: Xylitol given regularly 3 times a day for 3 months during the respiratory infection season failed to prevent AOM.