AIM To investigate the prevalence of salivary mutans streptococci (MS) in children from a low socioeconomic multicultural suburban area and to evaluate if a 3-year comprehensive oral health education (OHE) program, initiated at the age of two years, had an impact on the saliva levels. STUDY DESIGN Prospective clinical trial. METHODS The material consisted of two cohorts of 6-year-old children from a suburban area in southern Sweden. One cohort (n=804) had participated in a OHE program with a focus on tooth brushing with fluoride toothpaste and flouride tablets added to the regular preventive care provided by the Public Dental Service. The second cohort (n=217) consisted of reference children only attending for regular dental care. Both cohorts were dominated by children with Arabic background. Salivary MS were evaluated by a chair-side test and caries was scored through clinical examinations. STATISTICS Analyses were performed with Chi square tests, Pearson correlation coefficients and odds ratio calculations. RESULTS The prevalence of salivary MS was high in both cohorts with approximately 90% harbouring the bacteria. One third of the children exhibited high counts (>10(6) CFU/ml) and there were no statistically significant differences between the groups. A statistically significant positive relationship between the levels of MS colonisation and caries prevalence was found in both cohorts. CONCLUSIONS A 3-year OHE program implemented at the age of two years did not affect the high levels of salivary MS displayed in 6-year-olds living in a multicultural high-caries area.