Gonadal dysgenesis is a condition characterized by streak gonads in subjects who present the phenotypic appearance of females. In pure gonadal dysgenesis, unlike Turner's syndrome, no associated somatic anomalies are found; the adult is of normal or above average stature and may have eunuchoidal proportions (Sohval, 1965). The term 'XY gonadal dysgenesis' refers to patients with pure gonadal dysgenesis who are chromosomal males (Federman, 1967). In contrast, the term 'dysgenetic male pseudohermaphroditism' refers to an incomplete form of maldevelopment of the embryonic testis in patients in whom varying degrees of masculinization and genital ambiguity are found either at birth or at the time of puberty (Table I). In this report we present a family in which three sibs have abnormal gonads and incomplete sexual development: two phenotypic females with pure gonadal dysgenesis and a phenotypic male with dysgenetic pseudohermaphroditism (Fig. 1 and 2: II.6; 11.7; II.8). These two entities have been reported in sibs on only one previous occasion (Barr et al., 1967).