We conducted a double-blind controlled study of the effect of brain gangliosides in amyotrophic lateral sclerosis. Nineteen patients received intramuscular gangliosides (40 mg/d) for 6 months, and 21 received placebo. The deterioration rates for approximately 120 clinical and electrophysiologic parameters of neuromuscular function were analyzed, but no statistically significant beneficial effect of the drug was demonstrated. However, the large coefficient of variation for each item indicated that a sample size of several hundred patients would have been necessary to exclude the possibility that the drug produced a 25% slowing of progression of the disease.