The vesico-sphincter dyssynergia is generally observed in paraplegic patients with supra sacral lesions (40% of our cases). The neurophysiologic basis of the vesico-sphincter dyssynergia are the field of controversies. The animal experimentations have shown that a section below the ponts, induce a neural reorganization, enough to produce a normal micturation, rising sacral short loop reflexes. The reality of such mechanism is discussed by different authors who consider a normal micturation as a brain stem reflex rather than a simple sacral reflex. These factors allow the authors to undergo a neurophysiologic, neuropharmacologic and urodynamic investigation, with the intention of shedding light on the pathophysiology of the vesico-sphincter dyssynergia in 20 cases of paraplegic patients. On the basis of our data the following conclusions were made: the importance of the polysynaptic reflexes evoked by cutaneous or vesical stimulation (below the neurologic lesions) on the different degrees of vesico-sphincter dyssynergia; the quality of voiding depends on the equilibrium between extension and flexor reflexes in paraplegic patients; the presence of a neural reorganization using short loop reflexes who are the expression of a complex system rather than a simple sacral reflex; the effect of chronic intrathecal morphinic drugs on the reflex equilibrium and the quality of voiding and the eventual relation between opiate receptors and vesical sphincter dyssynergia.