We described 6 patients (from 3 families) affected with cerebrotendinous xanthomatosis (CTX). All are Sephardic Jews of Moroccan extraction. In view of the small number of CTX patients diagnosed in the world (a total of 50 including our 6 patients), we are probably dealing with an ethnic subgroup with a high CTX gene frequency, which we have estimated to be 1/108. Since there are differences in expression in this disease, we recommend cholestanol study in cases of undiagnosed cataract or tendinous xanthomas in childhood or early adolescence. The diagnosis in CTX is important not only for genetic counseling, but also in veiw of possible treatment.