Lateral and frontal tomography are indispensable in the study of the anatomy of the clivus. This shows a slight longitudinal posterior concavity in most cases. Abnormally marked concavity of the clivus is found not only in posterior fossa tumors but also in supratentorial neoplasms and in other conditions causing longstanding increased intracranial pressure. Occasionally it may be possible to demonstrate radiographically the spreading apart of the jugular tubercles in cases of chronic increased intracranial pressure. Clivus meningiomas frequently cause increased density of the bone structure but never bone erosion. Clivus chordomas, on the other hand, very frequently destroy the underlying and surrounding bone and in addition they show calcification. Discrete bone involvement can be recognized with frontal tomography. The value of frontal tomography in the study of congenital malformations of the clivus region is stressed. Lateral and frontal tomography are indispensable in the study of the anatomy of the clivus. This shows a slight longitudinal posterior concavity in most cases. Abnormally marked concavity of the clivus is found not only in posterior fossa tumors but also in supratentorial neoplasms and in other conditions causing longstanding increased intracranial pressure. Occasionally it may be possible to demonstrate radiographically the spreading apart of the jugular tubercles in cases of chronic increased intracranial pressure. Clivus meningiomas frequently cause increased density of the bone structure but never bone erosion. Clivus chordomas, on the other hand, very frequently destroy the underlying and surrounding bone and in addition they show calcification. Discrete bone involvement can be recognized with frontal tomography. The value of frontal tomography in the study of congenital malformations of the clivus region is stressed.