A survey aiming at assessing the frequency and the distribution of serological syphilis has been carried out on a sample of 6049 subjects aged 6-18 years in Mauritania. 33.4% of the samples had a reciprocal titer of 150 or more as determined by means of an immunofluorescence technique. However, frequencies in the different villages ranged from 7.5 to 47.6% and were strongly associated with the percentage of Black elements in the community. A significant difference was found between the age-groups 6-13 and 14-18, with a mean increase of 56%. These results suggest that an intervention program might be necessary in Mauritania.