Amyotrophic lateral sclerosis is usually considered a disease that will have a fatal termination in 1 to 3 years. A prospective study of 100 patients with this disorder revealed that 20 of them were living 5 years after the onset of their disorder. Review of other published series reveals that patients have been reported who lived for longer than 5 years and have then usually been reported as atypical cases, although the only way in which they are described as atypical is the duration of the disease. It is our assumption, based on these data as well as on additional clinical observations, that many patients with amyotrophic lateral sclerosis live for longer than 5 years and, rarely, they may have remissions of their illness. The possible significance of these observations is discussed.