PURPOSE: The purpose of this paper was to undertake a systematic review about the relationship between obesity in childhood, adolescence and/or adulthood and the prevalence of dental caries. METHODS: The authors searched Bireme, Medline, ISI, Cochrane Library and the internet for papers from 1984-2004. The main search terms were 'obesity' and 'dental caries'. The inclusion criteria were studies that defined obesity (body mass index) and dental caries (total number of decayed, and filled teeth - DFT/DFS/dft/dfs) in their subjects. The following were excluded from this paper: articles on reviews, dietary guidelines, policy statements, papers related to oral health and nutrition deficiency--underweight, and with no relation between obesity and dental caries prevalence or dental health problems. RESULTS: No systematic review has focused on correlating obesity and caries and only three stud ies had high levels of evidence. CONCLUSION: Only one study with high level of evidence showed direct association between obesity and dental caries. In view of the findings, further well-designed randomised studies are needed to demonstrate the relationship between dental caries and obesity.