We investigated the effect of increased middle ear pressure on blood flow to the inner ear, middle ear, and facial nerve in guinea pigs using a nonradioactive microsphere technique. The elevation of middle ear pressure significantly reduced blood flow to the middle ear. Blood flow to the facial nerve also decreased due to the elevation of the middle ear pressure but the reduction was not significant. Blood flow to the inner ear did not change even after the middle ear pressure was increased. Findings are discussed in relationship to aural barotrauma, alternobaric vertigo and facial baroparesis.