The aim of this study was to prevent or delay the transmission of cariogenic bacteria, and hence the early development of caries in children, by preventive methods targeted at the mother. This field study was carried out in rural southeastern Anatolia, Turkey, where access to dental care is limited. Twenty-seven mother-infant pairs were followed for 2 years. The infants were between 2 and 18 months old when the study began. Mothers in the control group (n = 12) received a simple care and advice program, and those in the test group (n = 15) followed a preventive and operative regimen. The occurrence and the incremental occurrence of caries in the mothers and children in both groups were determined annually. Using a commercial kit, levels of mutans streptococci and lactobacilli in saliva and plaque were measured in the children at 6-month intervals. The microbial data demonstrated that the children of mothers in the test group had significant reductions in mutans streptococci and lactobacilli in plaque (P< 0.001), whereas no such trend was observed in control children during the 24-month monitoring period (P> 0.05). After 12 months, the occurrence of caries (dfs) was significantly lower in the test group than in the control group (0.13+/-0.35 vs 1.67+/-1.30, respectively; P< 0.001). A similar difference was observed after 24 months (0.2+/-0.56 vs 3.17+/-1.70, respectively; P< 0.001). The results of this 2-year study demonstrate that a preventive and operative regimen designed to reduce oral bacterial levels in mothers can be remarkably effective in reducing the incidence of caries in infants in rural southeastern Anatolia. Owing to the prevalence of a traditional lifestyle based on close-knit families and clans, this region is an advantageous environment for the reduction of bacterial transmission from mother to child, while largely excluding other sources of infection for the child.