Xylitol prevents otitis media when given to children regularly five times per day. To find a more convenient dosing schedule, an enzymatic assay was used to measure xylitol concentrations in the saliva of 65 children after giving them xylitol chewing gum or syrup in doses equal to those used in clinical trials. Although concentrations high enough to have an antimicrobial effect were attained, the xylitol disappeared from the saliva within 15 min. This finding indicates that high peak concentrations are more important for efficacy than the amount of time the xylitol concentration exceeds that needed to produce an antimicrobial effect. A schedule with the same single doses given less frequently could be clinically effective in preventing otitis media.