This investigations is carried out order to find out the caries prevalence in a population affected by the Down syndrome. The rates obtained to fulfill this objective were CAOD and CAOS for the permanent dentition, and COD and COS for the temporary one. A total of 95 pupils between 6 and 21 years old were examined. 3 groups according to the age were established: the first one between 6 and 8 years old, the one between 9 and 13 years old and the third one between 14 and 21 years old. The following percentages were set for each age group and for boys and girls separately: Carious surfaces in permanent dentition, carious surfaces in temporal dentition, obturated surfaces in permanent dentition, obturated surfaces in temporal dentition and missing surfaces. The results indicate that the caries prevalence in these patients is similar to that obtained in other studies. Nevertheless, the number of obturations found is much smaller.