A review is given of the role of electromyography (EMG) for diagnosis, pathophysiological description and monitoring of patients with disorders of the peripheral nervous system. Various EMG methods are presented and their principal differences are discussed. The usefulness of these methods varies depending on the pathology to be studied. With modern quantitative methods for analysis, EMG has become more sensitive and accurate and is therefore an important part in the evaluation of the neurologic patient. EMG results are usually combined with findings from other neurophysiological investigations (neurography, evoked potentials), histochemistry, biochemistry and most importantly with the clinical signs to give as complete a picture of the condition as possible. The usefulness of EMG depends on a number of factors other than the quality of the investigation as such. These aspects are discussed briefly.