Five men with degenerative neuromuscular diseases (three with amyotrophic lateral sclerosis [ALS] and two with Duchenne's muscular dystrophy [DMD]) who had respiratory failure were treated with intermittent negative pressure ventilation (NPV). One patient with ALS in severe acute respiratory failure was successfully treated with NPV alone. This patient and two other ALS patients in chronic respiratory failure with PaCO2 elevation stabilized or improved their vital capacity (VC) and lowered their PaCO2 after 5 to 11 weeks of therapy. Finally, intermittent NPV was used to replace 24-hour positive pressure ventilation in two patients with DMD. It is concluded that intermittent NPV may stabilize or temporarily improve the respiratory status in patients with progressive neuromuscular diseases.