In the last few years, examination of the midline cerebral ventricles with opaque materials has been recommended by several authors (1–4). In the majority of cases requiring the use of contrast agents in the ventricular system of the brain, air or oxygen is sufficient to establish the exact position of the third ventricle, aqueduct of Sylvius, and fourth ventricle. Occasionally, however, this cannot be accomplished by either lumbar puncture or direct delivery of gas by ventriculography. The opaque contrast technic consists in placing usually no more than 1 to 2 c.c. of Pantopaque in a lateral ventricle through a ventricular catheter. The material is then advanced to the frontal horn under fluoroscopic control. As the head is slowly extended, Pantopaque drops first through the foramen of Monro into the third ventricle. With further elevation of the chin, contrast material rolls into the aqueduct and fourth ventricle. In the past, radiographic spot-filming of Pantopaque was carried out in conjunction with fluoroscopy. At times, the medium will pass through the aqueduct into the fourth ventricle at a rate too rapid for adequate spot-filming. The Pantopaque may also enter the subarachnoid spaces through the foramina of the fourth ventricle, necessitating difficult remanipulation or the introduction of more contrast agent. The examination is usually carried out immediately after unsuccessful air ventriculography and the patient may not be able to co-operate well due either to the lesion present or the sedation used. It has been found that these difficulties can be overcome, completely or in a large part, by the use of cinefluorographic technics. With the patient in the sitting position or prone, when necessary, anteroposterior and lateral projections can be made with either 35-mm. or 16-mm. movie film. In most of the cases examined by this means, both obvious and subtle deformities of the contrast column could be seen. In several instances, knowledge of the exact distance of the contrast-filled aqueduct from a landmark, such as the sella turcica, was helpful in establishing the presence of a pontine or cerebellar tumor. The 5-inch image-amplifier field has been found large enough to include the sella turcica, clivus, and petrous pyramids. When these images and the contrast-filled aqueduct or fourth ventricle are projected on a movie screen, measurements, adjusted for magnification, can be made. The values can be correlated with normal distances between the aqueduct or fourth ventricle and bony structures mentioned on the floor of the skull. To date the technic has been used in 8 cases with a high percentage of accuracy. Figure 1, A-C, records the course of the contrast material from a frontal horn into the third ventricle and aqueduct in a patient in whom an intracerebellar hematoma after trauma was found. The last movie frame in the sequence shows kinking of the aqueduct compatible with a space-occupying defect in the cerebellum.