A more accurate observation of retina and vessels was made by the fluorescence angiograms than the ones made by ophthalmoscope and routine colour photography. The method proved to be the most effective in detecting the soft exudates caused by increase in permeability and damage of arteriole walls. The soft exudate revealed by this method occur in many hypertensive patients with abnormal ECG. Also, new vessels are revealed in detail, and microaneurysma showed up as whitepoints. No conspicuous difference was observed in the measurement of the caliber of artery and vein of a normal person either by color of fluorescein photography. The differences, however, become greater as copper wire artery and silver wire artery. Namely, the vessels we observe are columns of blood since the walls of blood vessels are transparent. According to the studies conducted by this method, however, it appears as though the fluorecein is coming through the interstices of endothel and depicting the walls of the vessels. Observation was also made on fluorescein photographs at the time of blood pressure raised by means of HCl-methoxy-amine (IV) and also at the time of blood pressure lowered by means of sodium nitrite treatment of a rabbit.