Xylitol has become a debated measure in caries prevention. This paper aims to examine and comment on some possible controversies, with emphasis on the most recent literature. A search for clinical trials was conducted through 2007 in PubMed, and papers describing a controlled xylitol intervention with reported endpoints were assessed. The main reasons for the conflicting results were weak study designs, underpowered groups, mixed outcome measures, and use of low-xylitol regimens. Definitive evidence for a caries-preventive effectiveness of xylitol is still lacking, and it is concluded that the controversies cannot be solved without well-designed double-blind randomized placebo-controlled caries trials in defined populations. Furthermore, as a candidate for public health intervention, the economical aspects of xylitol administration must be taken into account at the planning stages of future projects. Until further evidence is available, xylitol should be regarded as an adjunct to other preventive measures in targeted individuals.