Respiratory insufficiency of restrictive origin, often aggravated by obstructive disorders, is constant in amyotrophic lateral sclerosis (ALS), and is usually progressive. Respiratory distress may be life-threatening while the neurologic disease is still limited. Furthermore, the diagnosis of ALS is not always obvious when urgent therapeutic decisions have to be made. Results are reported in 16 patients with ALS treated by assisted ventilation: 14 by endotracheal and 2 by nasobuccal routes. Transient improvement in respiratory function in 9 patients allowed partial return of spontaneous respiration. Known mean duration of course (n = 14) from first sign to death (12 cases) or last control (2 cases) was 3 years 3 months (1 to 9 years). Survival from tracheotomy to death or last control (July 1988 in 12 cases) was 12 months (3 to 48 months). These patients can now return home under the care of associations providing respirators.