A case of Tay-Sachs diseases in a Negro child is reported. The occurrence of this disease in non-Jewish individuals is very rare and this is the fifth case of a Negro-child reported in the litterature. Some genetical aspects are studied and the authors conclude that the frequency calculation of the mutant gene is impossible due to the small number of cases and to the fact that there is reliable information regarding the rate of birth of Negro individuals in the general population. The diagnosis was based on ophtalmological and clinical data. No specific biochemical tests were performed but the data obtained are congruent with other cases reported in the litterature.