The symptoms of amyotrophic lateral sclerosis (ALS) include:

• Weakness or clumsiness in the hands and feet.
• Gradual loss of strength of the arms and legs.
• Inability to control the use of the arms and legs.
• Muscle twitches (fasciculations).
• A stiff, clumsy walking style.
• Difficulty swallowing, speaking, and breathing. You may notice a problem with drooling.
• Fatigue.
• Trouble controlling your emotions. You may burst into tears or start laughing for no reason.
• Muscle cramps, especially at night, which may occur late in the course of the disease.
• Pain during the late stages of the disease.

Your ability to think, reason, and remember will most likely not be affected by the disease.

It is important to remember that having muscle weakness, fatigue, stiffness, and twitching doesn't necessarily mean that you have ALS.

The first sign of ALS is usually slight weakness in one leg, one hand, the face, or the tongue. Other problems may include increasing clumsiness and difficulty performing tasks that require precise movements of the fingers and hands. Muscle twitching may also occur. The weakness slowly spreads to the arms and legs over a period of months or years. As the nerves continue to waste away and decrease in number, the muscle cells that would normally be stimulated by those nerves also start to waste away, and the muscles weaken.

ALS is a progressive, disabling disease. Walking, speaking, eating, swallowing, breathing, and other basic functions become more difficult with time. These problems can lead to injury, illness, and other complications.

Respiratory problems are the most common serious complication of ALS. As the muscles in the throat and chest area become weak, swallowing and coughing become more difficult, which may sometimes cause food and saliva to be inhaled into the windpipe (aspiration). This may lead to pneumonia. Breathing problems tend to get worse as the disease progresses, increasing the risk of infection and respiratory failure.

Pneumonia, pulmonary embolism, lung failure, and heart failure (probably due to lack of adequate breathing as the chest muscles weaken) are the most common causes of death among people with ALS. In most cases, death will occur within 3 to 5 years after symptoms begin, although some people live for many years, even decades.