Fluoride mouthrinses have been used extensively for the past 15 years to prevent dental caries in children. Their use has been especially widespread in organized school-based programs in the US. Nearly three dozen clinical studies of fluoride mouthrinses, both with and without placebo controls, have been reported in the literature since the early 1960s. The overwhelming majority of those studies report statistically significant caries inhibition from the use of the products. Most of the studies were published prior to the knowledge of a decline in caries prevalence during the past 30 years. Consequently, the results of those studies lacking a placebo control group have been challenged. Even randomized clinical trials with appropriate control groups appear to be reporting declining differences between test and control groups. Using a model based on annual caries increments from published studies, the conclusion is reached that future use of fluoride mouthrinses is unlikely to result in annual savings in DMF increment greater than 0.4 surfaces, regardless of age of rinsers.