Two cases of Morvan's chorea are reported. One of the patients presented the characteristic of having had two attacks, the first after organic mercury preparations, and the second after gold salts for inflammatory rheumatism. The second case had facial fibrillations only, and this was followed by a regressive polyradiculoneuritis one month later. This latter case raises certain diagnostic problems. The existence of a particular type of immuno-allergic tendency could be validly related to a triggering effect of various etiological agents (metals such as mercury or gold salts, or infective agents). The absence of hypotonia, and a regressive course appear to be the characteristics that distinguish fibrillary chorea from the continuous activity syndrome of the muscle fibers described by Isaacs.