The authors studied 102 clinical observations of patients presenting the symptoms of amyotrophic lateral sclerosis (Charcot's disease). Two distinct groups were discerned from an analysis of the ages of onset: the first group, comprising 20 patients, represents the juvenile form, with onset before the age of 30. The second group (82 patients) represents the classic form of Charcot's disease. Generally speaking, the adult group is identical to that reported in the literature since Charcot first described amyotrophic lateral sclerosis. The incidence is greater in males. Hyperproteinorachia is frequent. No local etiologic cause has been identified. The apparent incidence of the disease in the regions of Tunis and Nabeul is 0,45 per 100 000 inhabitants per year. The juvenile form is characterized by a relative frequency of the familial form (30 p. 100), a possible association with particular sensory symptoms, and a slow evolution. Hypoproteinorachia is relatively frequent. The authors discuss the relations between these two groups of amyotrophic lateral sclerosis. Are they two different expressions of the same disease, or are they two different diseases?