Fatigue is one of the most common medical complaints. Sometimes, fatigue is chronic, unexplained and induces significant distress or impairment in social, occupational or other important areas of functioning. This condition was described as neurasthenia by Beard at the end of the 19th Century; more recently the United States Centers for Disease Control and Prevention (CDC) suggested to call it "Chronic Fatigue Syndrome" (SFC). Both are considered as physical diseases and share certain therapeutic measures. Pathophysiology is still unknown and may involve viral agents, immunological processes or psychiatric disorders. Similarly most of the treatments which have been properly evaluated seem to be more or less inefficacious.