The term of the chronic fatigue syndrome (CFS) appeared in the 20th century for the first time and it represents a diagnostic, therapeutic and socio-economic problem from the very beginning. In recent years, the term of the chronic fatigue and immune dysfunction syndrome (CFIDS) is often used as far as the disorder of the immune system is diagnosed in a patient. In relation to the CFS, we can find also the term of fibromyalgia and postviral fatigue syndrome (PFS), they are described as subgroups of the CFS. According to the current medical knowledge, the so-called “emergency diagnosis“ is attributed to the CFS. So far, it is not clearly decided whether it is a disease or nonspecific symptoms which may precede the manifestation of a specific disease for a couple of years, namely autoimmune, tumorous, endocrine, metabolic or infectious one. CFS has not been recognized as a diagnosis by the WHO, consequently it was not included in the 10th International Classification of Diseases. Accordingly, it is still considered a syndrome, i. e. the sample of objective and subjective symptoms which we are not able to classify precisely as a diagnosis and which may occur in relation to different diseases. The article includes the update review of current views on the CFS. Etiology, pathogenesis, diagnostics is mentioned, the possibilities of therapeutic interventions are roughly presented and finally the issue of the CFS in review medicine is mentioned.

        Key words: fatigue – chronic fatigue syndrome – chronic fatigue and immune dysfunction syndrome – postinfectious fatigue syndrome – fibromyalgia