Unilateral atrophic cerebral lesions occurring early in life frequently produce cranial asymmetry that may easily be detected in plain skull radiographs; This asymmetry consists in ipsilateral decrease in size of the cranial chamber and often increased size of the paranasal sinuses and mastoid air cells. Such examinations should never be omitted in the study of the epileptic patient.In many cases of posttraumatic epilepsy ordinary skull radiographs reveal no localizing information but tears and deficiencies of the dura tend to produce characteristic changes and occasionally point out the exact site of a previous skull injury.Carefully performed encephalography should be undertaken in almost all cases in which focal cerebral atrophy is suspected. The general region where the epileptogenic lesion will be found is frequently shown by this method. Occasionally a focal atrophic lesion may be present although encephalography is negative. This is rare and usually a normal encephalogram is a strong contraindication to craniotomy unless the other evidence available is very convincing.The exact site of a focal epileptic lesion can usually not be determined by radiographic examinations alone, although the general region can be ascertained in most instances. Careful correlation of the clinical, electrographic and radiographic findings is essential.Cerebral arteriography is occasionally a helpful procedure in the diagnosis of focal epilepsy, particularly when aneurism or hemangioma is suspected.