The effect of elevation of inner ear pressure on cochlear blood flow in guinea pigs was studied with use of nonradioactive microspheres and a laser-Doppler flowmeter. Hydrostatic pressure was applied to the perilymph through a glass capillary tube inserted into the scala tympani of the basal turn. Because of the elevation of the inner ear pressure, the cochlear blood flow, except to the modiolus, decreased significantly. Above all, the blood flow in the capillaries or microcirculation in the cochlea was most easily impaired by the elevation of inner ear pressure.