Failure of the respiratory system is the most common cause of death in amyotrophic lateral sclerosis. This is due to weakened respiratory musculature resulting in respiratory failure, ineffective cough, and failure to protect the lungs from aspiration. Treatment is only supportive at present, but mechanical ventilation with either negative or positive pressure offer some life-extending possibilities. The respiratory system should be closely monitored as early identification of problems may allow better insight into the immediate prognosis.