In the course of acute glomerulonephritis and less commonly in other varieties of chronic interstitial nephritis, there may occur acute episodes of cerebral phenomena, such as epileptiform convulsions, coma, headache, amaurosis, hemiplegia and aphasia. In the past, these episodes were generally included under the concept of uremia and were termed acute uremia. Since the beginning of the present century, convincing evidence that these cerebral episodes are not uremic in nature has gradually accumulated. This evidence will be summarized later in the paper. It has become clear that these cerebral symptoms are correlated with hypertension, being a manifestation of circulatory disturbances in the brain consequent on the hypertension. For this reason, we have termed the cerebral syndrome the hypertensive encephalopathy. The nature of the hypertensive encephalopathy is well illustrated in the following case. We have had the patient under continuous observation over a period of twenty months at the Mount Sinai