Amyotrophic lateral sclerosis, ALS, is a common form of motor neuron disease that involves a loss of function in upper and lower motor neurons. ALS causes a progressive loss of muscle function that frequently initiates in the limbs, called limb-onset ALS, or initiates in facial muscles, called bulbar-onset ALS. This book describes the current understanding of ALS symptoms, diagnosis, causes, and treatments. Initial symptoms vary in type of muscle dysfunction, intensity of symptoms, and speed of disease progression. Diagnosis requires loss of function in both upper and lower motor neurons for limb- and bulbar-onset ALS, distinguishing ALS from other neuromuscular diseases. Although no cause or initial trigger has been determined for ALS, eventually both limb and bulbar muscles will show dysfunction as the disease progresses. In later stages of the disease, muscle dysfunction typically leads to respiratory failure and death. Management of neurotransmitter levels in patients can prolong life by months, but no cure exits for the disease. Other treatments exist that can help patients manage muscle weakness or spasms as the disease progresses. The book concludes by considering future detection, treatment, and diagnostic approaches with the goal of preventing disease initiation or progression.