Neuromuscular respiratory failure is the cause of death in the majority of patients with ALS. Respiratory muscle dysfunction impacts on quality of life and survival. Attentive management of respiratory muscle weakness is an important aspect of the management of the ALS patient. The respiratory muscles may be thought of as four functional groups: the inspiratory muscles, the expiratory muscles, the accessory muscles of respiration, and the upper airway muscles. This paper will review the structure and function of the neuromuscular respiratory system, and the evaluation and management of respiratory muscle dysfunction in ALS patients.