The forebrains of various snakes were examined by electron microscopy. In the forebrain of Elaphe quadrivirgata, the banded structures were found within the perivascular basement membrane in the proximity of neural elements. These structures were composed of numerous fine filaments, 60-70Å in diameter, running parallel to the blood vessel. Regularly repeated dense bands occur in crossing over the structures at interval of about 1, 700Å. Sometimes a cluster of collagenous fibrils were located close to the banded structures, and some of the fibrils entered into them.Although the real chemical nature of these structures was not known, it was assumed that the structures are composed of collagenous components.The observation in the snake injected with iron dextran, demonstrated the existence of the blood-brain barrier in the snake, but did not suggest that the banded structures play any active role in lowering the blood-brain barrier of the snake. However, the fact that these banded structures were observed only in Ealphe quadrivirgata among snakes, shows differences in structure and therefore probably in function of the circulatory system in brain tissue in animals species.