With the purpose to study the experimental cerebral hemorrhage from histopathological and histochemical aspects, a series of experiments was conducted with the brain of 25 male rabbits (weighing about 3kg) after experimentally inducing renal hypertension by a modification of Goldblatt's method, and changes in the local metabolism of various cerebral tissue components, were studied. The results are briefly summarized as follows. 1. In the rabbits with experimental hypertension induced by a modified method of Goldblatt the rate of cerebral hemorrhage was as high as 60% , namely, in 15 out of the 25 animals. Histologically, all the bleeding cases showed principal hemorrhagic focus and ball hemorrhages around the lesion. In addition, there were recognized fibrinoid necrosis of varying degrees in arterioles, and in a few cases the distension of arterioles which looked like aneurysm, showing bleeding at the tip of the distension. 2. By histochemical staining, enzymic activities of the bleeding brain was studied. As a result it was found that the nerve cells or perikaryon and neuropil of the cerebral cortex and subcortical nuclei, as well as glia cells of the white matter showed some differences in their enzymic activities. However, in general the activity of phosphorylase of the glycogen cycle, lactic dehydrogenase of Embden-Meyerhof pathway, glucose-6-phosphate dehydrogenase of Warburg-Dickens cycle, and DPN-diaphorase activity of the ion transport system were accelerated. In contrast, the activities of succinic dehydrogenase and malic dehydrogenase of TCA cycle were diminished. Furthermore, a marked decrease in the activity of acid phosphatase of nerve cells suggested a considerable decrement in the cell function. In the cases where the thickening of the wall of arterioles were observable, there could be seen an increase in all the enzymic activities of the metabolic pathways, such as phosphorylase, lactic dehydrogenase, glucose-6-phosphate dehydrogenase, succinic dehydrogenase, malic dehydrogenase, and DPN-diaphorase. This is an interesting finding as compared with the cases with derangement of the wall structures of arterioles by fibrinoid necrosis where it was proven histologically that all the activities of the enzymes were diminished or obliterated. The activities of alkaline phosphatase and adenosine triphosphatase of the hydrolytic enzyme system was markedly decreased in the capillaries and arterioles with derangement of wall structures and the thickening of the vessel wall. This indicated the destruction of the blood-brain barrier due to the acceleration in the permeability of the membranous structure, and this suggests that it is concerned with both the brain swelling as observed macroscopically in the bleeding brain and the metabolic disturbances in nerve cells as mentioned in the foregoing. As described thus far, histologically the findings obtained in this experiment do not differ much from those in the available literature, but histochemically many new findings have been obtained as regards local metabolic changes of enzymic activities.