The mode of inheritance of primary gonadotropic deficiency was studied in 38 children and adolescents. 92% of this population was male with high frequencies of undescended testes (80%) and micropenis (31 %). Anosmia was present in 61 % of the patients aged more than 5 years and was a frequent genetic marker in the families. Inheritance was matrilineal in 18, X-linked dominant or autosomal dominant in 6. In 13 cases, the transmission was patrilineal and evoked autosomal dominant inheritance. An autosomal recessive transmission was likely in 7 patients. The data agree with the suggestion of multiple modes of inheritance of congenital gonadotropic deficiency, and clearly show the wide range of expressivity of the disorder.