Electrotherapy is defined as the sum of therapeutic modalities of physical medicine capable to change the threshold of elicitation of nerve or muscle. Classification due to applied pulse frequencies, way of action of transcutaneous nerve stimulation (= TENS) and of iontophoresis is described. Pain syndromes, muscle atrophy by loss of activity and support of wound healing are named as accepted indications for electrotherapy. The difficulties of electrical stimulation of paretic muscles and the problem, whether different indications for certain forms of electrotherapy exist or not, is discussed.