Blood vessels on Reissner's membrane were electron-microscopically found in 24 out of 30 rats of the Wistar strain. The vessels were noted in the upper turns, mainly in the third turn of the cochlea. They originated from radiating arterioles in the upper spiral ligament and took straight courses radially down to the spiral limbus, and further to the modiolus, running along the surface of the scala vestibuli side of the membrane. Their diameter was approximately 4 microns. Bifurcated blood vessels were occasionally detected in 3 out of the 24 rats that possessed the vessels in the membrane. From the morphological point of view the blood vessels in Reissner's membrane may possibly have some function in the inner ear of the rat.