In anesthetized cats, distension of the urinary bladder induces powerful reflexes in postganglionic sympathetic neurones projecting to the hindlimb: muscle vasoconstrictor neurones (MVC) are excited and cutaneous vasoconstrictor neurones (CVC) are inhibited. We investigated these reflexes quantitatively before and after sacral rhizotomy. The reflex responses in MVC and CVC neurones were completely abolished after elimination of the pelvic afferent input demonstrating that these reflexes are generated exclusively by excitation of sacral bladder afferents. The activation of lumbar bladder afferents which are supposed to be able to elicit painful sensations did not contribute to vesico-sympathetic reflexes in MVC and CVC neurones.