Amyotrophic lateral sclerosis is characterized by degeneration of the motor neurones in the central nervous system and, as a rule, the condition results in rapid incapacity and death. The etiology is unknown but experimental results from recent years suggest that immunological mechanisms are of pathophysiological significance. Gangliosides constitute an important membrane component in nerve tissue and the majority of patients probably have high titres of circulation polyclonal IgM-antibodies to these compounds, particularly gangliosides GM1 and GD1a. The antibody titre appears to be correlated with the clinical condition and selective immune suppression (e.g. with cyclophosphamide) may possibly be of therapeutic value.