In 1890, Morvan described a syndrome of myokimia associated with muscle pain, excessive sweating and sleep disorders. The course was severe and the patient died five weeks after the onset. Several cases were published after this first report in the French literature. The last for 10 years the disease seems to have disappeared. In fact, it seems that the progress in electromyography introduced clear definitions of spontaneous muscle discharges (myokimia, neuromyotonic discharges, fibrillations, fasciculations) allowing recognition of a disease characterized by a syndrome of spontaneous and continuous muscle fiber activity associated with cramping, slow relaxation (pseudomyotonia), excessive sweating and stiffness. Different terms have been used to describe this entity: neuromyotonia (Mertens and Zschocke, 1965) or continuous muscle fibre activity (Isaacs, 1961). Classification of these syndromes has to distinguish inherited from acquired forms, idiopathic cases from cases where neuromyotonia is associated with a peripheral neuropathy, a cancer or an immunological disease. Moreover, the frequent occurrence of this later association and recent reports of improvement after plasma exchanges suggest a possible autoimmune aetiology for this group. Finally, we suggest that the term of "Maladie de Morvan" must be used instead of chorée fibrillaire but only concerning patients who exhibit central disorders including insomnia, hallucinations and altered behaviour.