The effective therapy of a disturbance of anal continence requires an adequate preoperative diagnostics. In most cases this includes some kind of neurophysiological investigation. Close cooperation between the internist, the surgeon and the neurologist is advantageous. The initial history, clinical examination and electromyography of the pelvic floor will usually be enough to differentiate between aetiologies. In the first phase it is necessary to decide whether the problem is neurogenic or muscular, and then to see localising signs for a nerve defect (central or peripheral) or, respectively, signs of a defect in the skeletal musculature. It must be said that a peripheral nerve lesion (eg. a stretching injury of branches of the pudendal nerve) and a muscular defect may be combined. At the end of the diagnostic process the surgeon or internist and neurologist must decide together whether the diagnosis is appropriate, and then whether an operative or non-operative approach to treatment is fitting. In the second phase of diagnosis are further neurophysiological investigations, which are only indicated in more special circumstances. These investigations include: nerve conduction velocities, reflex latencies (anal-, bulbocavernosus-, and pudendoanal reflexes), evoked potentials, and the single fibre EMG to determine fibre density. These neurophysiological investigation in proctology allows the clinician a wider scope of diagnostic possibilities, which should lead to more sensible therapeutic options being taken.