This paper aims at shewing the author's experience after 20 years of existence of the Myopathies out-patient clinic, which would better be called out-patient service for diseases of the motor unit. After giving the currently used classification, with 13 items and 95 affections, the author refers only his experience and items over which there is - or not - agreement with the existent literature. Attention is called specially to the value of electromyography and muscle biopsies, both of which are tests which, on their own, are of very little help to the diagnosis. The scope of this paper is not to describe the clinical picture of the different afections, but only to give the collaboration of the author's experience so that specialists in Neurology may profit from the practical data verified in about 2000 patients.