The impaired formation of the diaphragma sellae may lead to the development of the empty-sella syndrome. This structure, when fully formed, is a protective barrier against the pulsating action that the cerebrospinal fluid exerts on the sellar content. There are anatomical features which support this belief, but they also suggest that the development of the diaphragma sellae is a factor which determines the morphology of the sella turcica and its contents. Those human specimens which do not have diaphragma sellae or in which it is only partially developed, are characterized by a smaller hypophysis, always located at the inferior and/or posterior half of the sella, with a larger sellar volume and frequently greater fragility of its bony walls. These findings, although rare (5% of the cases), are indirect signs of the important role which the diaphragma sellae plays in the sellar region.