In this report cerebro-cortical innervation of the urinary bladder has been investigated in man by the use of electroencephalography and in the cat by the application of the evoked potential technique. Electroencephalographic monitoring during bladder filling while the patient was asleep was a useful method to determine cerebral response to stimulation of bladder sensory receptors. Bladder filling was performed during stage IV sleep. In the intact individual detrusor reflex contraction or attainment of bladder capacity was followed by prompt arousal and desynchronization of EEG rhythms. In patients with interruption of bladder sensory pathways in the periphery or in the spinal cord there was loss of impairment of the EEG response to bladder filling. In the cat, anesthetized with sodium pentobarbital, electrical stimulation of the nerve supply to the urinary detrusor muscle and to the pudendal nerve innervation to the periurethral striated muscle and anal sphincter, evoked a diphasic response in the cerebral cortex of the frontal lobe. All responses were grouped in the same area and were of short latency. Similar potentials have been evoked in man. These studies demonstrate that the peripheral, spinal and cerebral innervation of the urinary bladder in man are definable by electrophysiologic techniques. As a result, these electrophysiologic techniques are applicable to defining neuropathic changes in the urinary bladder innervation in man.