Transurethral electroresection of external urethral sphincter (TUR-sph) was performed in sixteen male tetraplegics to obtain good voiding efficiency and to prevent autonomic dysreflexia due to detrusor sphincter dyssynergia. Ratio of residual urine as a parameter of voiding efficiency and blood pressure and plasma noradrenaline level during voiding as parameters of the significance of autonomic dysreflexia were evaluated before and after TUR-sph, and all these parameters had significantly improved after TUR-sph. After discharge from the hospital, all patients urinated comfortably with the maneuver of suprapubic percussion by themselves and/or their helpmates, and no patients complained of any inconvenience due to urinary incontinence. Moreover, no patients had the episode of autonomic dysreflexia in daily life except for one patient who had it once with urinary tract infection. TUR-sph brings not only the improvement of voiding efficiency but also the effect as a safety valve against autonomic dysreflexia by means of preventing the occurrence of autonomic dysreflexia due to detrusor sphincter dyssynergia.