Very high intravenous doses (2-19 mg/min) of thyrotropin-releasing hormone (TRH, L-pyroglutamyl-L-histidyl-L-prolinamide) given to 12 patients with amyotrophic lateral sclerosis (ALS) produced a moderate to marked improvement of functions caused by deficiency of lower motor neurons (weakness) and upper motor neurons (spasticity). The improvement was sustained throughout the infusion and for about 1 h thereafter; sometimes a slight improvement was evident 20 h after infusion.