Myoclonus epilepsy is a rare, but well recognized, clinical entity characterized by the occurrence of rapid, abrupt, irregular, jerky, involuntary contractions in one or several muscle groups, associated with generalized convulsions. Those afflicted with the disorder usually give a familial history of it or of essential epilepsy or of some other degenerative disease of the central nervous system. Several clinical entities characterized by the presence of myoclonic movements have been described, such as paramyoclonus multiplex of Friedreich,1 intermittent myoclonia of Lundborg,2 partial continuous myoclonia of Kozhevnikoff3 and progressive familial myoclonia of Unverricht.4 As in the case of many other degenerative diseases of the central nervous system, the forms mentioned are possibly variants of the same condition, some with and others without a hereditary or familial history. In addition to descriptions of the more common familial and hereditary forms, the literature contains reports of cases in some