Most patients with neurogenic impotence present with a pre-existing neurologic disease. The neurologic assessment in these patients is generally performed to confirm that the underlying neuropathology plays a role in the erectile dysfunction. There are patients, however, with no obvious pre-existing neuropathology who are identified as having a vibratory impairment of the dorsal nerve on penile biothesiometry. Subsequent neurophysiologic testing in several of these patients has confirmed unsuspected neuropathology. An objective evaluation of autonomic cavernosal neurointegrity is still awaited. Such a test may enable the detection of efferent denervation resulting in neurogenic erectile dysfunction that is not clinically obvious.