Cerebral edema in both the human and experimental animal will be studied by means of axial computerized tomography using the EMI scanner. An attempt will be made to correlate tissue densities as determined by this technique with histologic patterns and chemical changes in the brain. The experimental studies will involve cryogenic cerebral injury in the rhesus monkey. The effect of postmortem changes will be studied in the human and under controlled conditions in the experimental animal. The attenuation properties of cerebral lipids will be studied in a phantom placed in the EMI scanner. In the human, with unilateral disease, changes in tissue density will be compared with differences in the weights of the hemisphere as well as histologic and chemical changes. In patients with bilateral disease, the results will be compared with changes in the ratio of skull and brain volume. From these studies, we hope to define a method for quantifying cerebral edema in the living patient from the EMI scan.