Objectives: To review the evidence of a relationship between sugar-containing methadone and dental caries. Data sources: A systematic search of Cochrane Library, PubMed, PsychINFO, EMBASE, MEDLINE, Current Controlled Trials, WHO, OHRN, SIGLE and ERIC databases was conducted from January 1978 up to June 2010. Study selection: Articles were assessed and data abstracted independently by two reviewers. Papers that provided information about methadone and dental caries and were written in English were included, regardless of type of publication, authors, source of financial support and outcomes. Nineteen articles were identified; of these only three contained quantitative evidence, one of which was a survey. Conclusions: Many people on oral methadone maintenance programmes have been reported to have high levels of dental caries. However, there is no strong evidence to support a direct link between sugar-containing methadone and an increase in dental caries. High quality studies are required to assess the potential adverse effects of methadone on oral health. (Contains 1 table and 1 figure.)