Among 135 consecutive cases of hypopituitary dwarfism, 42 related to detectable intracranial tumour or defect. In 13 cases the tumour had been previously operated and/or irradiated. In 29 others the defect was suggested by neurological abnormalities or headache, skull radiographs, ocular examination or by associated post-hypophyseal deficiency and was demonstrated by pneumoencephalography. When none of these associated abnormalities was found, pneumoencephalography failed to demonstrate any intracranial lesion. Among the 93 so-called idiopathic cases there was a large majority of males (60/93) with a history of birth difficulties (34/60) and especially of breech delivery (23/60). TSH, FSH/LH and ACTH deficiencies were associated to GH deficiency in 81% of patients with detectable intracranial lesions, 57% of male and 39% of female idiopathic cases. The number of patients with idiopathic isolated GH deficiency was similar in boys and girls, suggesting in them the hypothesis of a recessive autosomic genetic defect in spite of the scarcity of familial cases. Peculiar clinical associations may contribute to the diagnosis.