There are various clinical neurophysiological techniques which have been applied to the investigation of the pelvic floor and neurogenic bladder. Sphincter electromyography (EMG) has proved to be particularly valuable in identifying patients with parkinsonism who have multiple system atrophy. EMG of the striated muscle of the urethral sphincter is essential in recognizing the abnormal spontaneous activity which causes urinary retention in young women. Tests which examine aspects of nerve conduction velocity have proved to be of lesser value both because such investigations test conduction of nerve fibres rather than levels of innervation, and furthermore examine large myelinated fibre conduction rather than that of the unmyelinated fibres which comprise the autonomic innervation.