It has been shown that neck muscle proprioceptors can inhibit vestibulospinal outflow at lumbosacral levels of the cord. The inhibition was abolished by decerebration, but was unaffected by ablation of the contiguous regions of the ectosylvian and suprasylvian gyri receiving vestibular projections. Descending vestibular effects on segmental lumbosacral reflexes were also examined. One effect only, a prolonged facilitation of the monosynaptic reflex, was abolished by decerebration. Unlike a similar effect obtainable from neck muscle proprioceptors, the facilitation survived acute ablation of the anterior poles of the suprasylvian and ectosyivian gyri.