Dental caries is becoming increasingly common in developing countries but very few attempts have been made to assess its prevalence accurately. We therefore carried out an epidemiological survey in 1998 in the south of Benin, to estimate the prevalence of dental caries in 300 school children, both boys and girls, aged 12 to 14 years. Each child underwent a dental examination and interview and the data obtained were recorded in a personal clinical record. We determined DMF index for various subgroups of children. We then analyzed DMF index and its correlation with sex, age, socioeconomic level, the urban or rural origin of the child, diet and daily dental hygiene practices. We found that mean DMF index at age 12 years was 0.83 (38.7% had dental caries and 4.4% had fillings), and thus, 61. 3% of the children were free of dental caries. We also found that 80% of the children had an accumulation of tartar. More boys than girls had dental caries. Rural children were less likely to have dental caries than urban children. The prevalence of caries appears to be low despite poor dental hygiene and a lack of dental treatment. These results conflict with those of most other studies. However, they should be interpreted with caution because the population studied was very homogeneous (selection bias), the age of the children could be no more than approximate (some were probably younger than 12 and others older than 14, because the registry system is inaccurate), there had been health education classes in some schools before the survey and it was difficult to define socioeconomic level and a sugary diet. For example, the lower socioeconomic level (no TV, radio, electricity or tap water) was probably an accurate representation of children from the rural area, whereas urban children were proud of being well-equipped and may have had a tendency to exaggerate. The prevalence of dental caries in this population is currently as low as that for most pre-industrial African countries. To avoid problems in the future, dental health services require reorganization and should stress measures for preventing dental caries: changes in dietary habits, the promotion of traditional tooth brushing practices, the systematic surveillance of dental caries at school and the removal of tartar.