SUMMARYThe genetic study of sterility, although rather complex, may be carried out, as far as the parents are concerned, on the basis of existing detection methods. A number of forms of individual sterility may be detected on the basis of the caryotype (ovarian and testicular dysgenesis, hermaphroditism), while a chromosomal pathologic phenotype is missing for others, and the corresponding genotypes must be detected through clinico-genealogical methods (pseudohermaphroditism, adrenogenital syndrome, Laurence-Moon-Bardet-Biedl syndrome, hereditary malformations). It is noted that the problem of immunitary incompatibility is not sufficiently clear. Examples are presented of others forms of sterility depending on a lethal load of theconceptus, for which consanguineous marriages may be held largely responsible. Cases of sterility may also be found in relation to mental diseases. The importance of eugenic counseling is stressed.