Activities of external vesical sphincters of thirty-eight patients with abnormal urination were studied by electromyography. Electromyography was studied on bulbocavernosus muscle in male subjects and on urethral striated muscle in female subjects. This report mainly deals with pathological electromyogram in case of cord injury and peripheral nerve injury. The following three points are thought to be the most important in electromyographic study of external vesical sphincter. (1) Spike discharges in EMG of external vesical sphincter in time of empty bladder. (2) Ability of voluntary interruption of urination (voluntary contraction of external vesical sphincter). (3) Increase or no increase of spike discharges in EMG of external vesical sphincter in time of full bladder (reflex contraction of external vesical sphincter). Abnormal electromyograms of external vesical sphincters sharply revealed patho-physiological states of the sphincters. Fibrillation voltage in time of empty bladder, no increase of spike discharges, and high amplitude or complex NMU voltage in time of reflex contraction as well as voluntary contraction of external vesical sphincter were seen in cases of peripheral nerve injuries or cord injuries .