Chronic fatigue syndrome (CFS) is characterized by a state of profound, persistent, and debilitating fatigue that significantly impairs daily activity level. It is associated with a variety of complaints, chiefly related to the neuromuscular, neuropsychiatric, and immunological systems. The goal of the diagnostic process for this disorder is to exclude more clearly definable disorders though traditional medical assessment as well as special studies and tests. This process employs specific diagnostic criteria, particularly those associated with the psychiatric, immunologic, infectious, and musculoskeletal aspects of the disorder.