Chronic Fatigue Syndrome (CFS) is long-term tiredness (fatigue) that does not go away with sleep, or rest, and affects everyday life.

CFS is also known as ME (myalgic encephalomyelitis). Myalgia is muscle pain, and encephalomyelitis is inflammation of the brain and spinal cord. ME is a commonly used term, although it can be thought to be too specific to cover all the symptoms.

CFS is the term that is often used to describe long-term tiredness by doctors and medical professionals. This is because in the majority of cases, the main symptom is chronic fatigue. This is usually the preferred term, rather than ME. In CFS, there is little evidence that inflammation of the brain and spinal cord occurs.

ME is often the preferred term of people who have CFS. This is due to the fact that they feel fatigue is too general and does not reflect the severity, and different types of fatigue. Also, it is felt that even though fatigue may occur in most cases, it is not the main, or only, symptom people experience.

Anyone can get CFS, although it is more common in women than in men. It usually develops in the early twenties to mid-forties. Children can also be affected, most commonly between the ages of 13-15.