Asthenia is a pathological condition characterized by abnormal, spontaneous fatigue that occurs without exercise, continues for a long time and does not go away after rest. With asthenia, performance decreases, and difficulties arise in maintaining prolonged mental and physical stress. The presence of these disorders is associated with a decrease in quality of life, an increase in morbidity and mortality in general. In general, we can say that complaints of weakness, tiredness and fatigue are the most common when visiting a primary care doctor. The article presents various clinical manifestations of asthenia, classification and features of these disorders. In clinical practice, it is important to distinguish between idiopathic chronic fatigue (primary or functional asthenia) and chronic fatigue syndrome (CFS). The publication presents modern diagnostic criteria for this syndrome. It has been shown that CFS should be distinguished from nonspecific chronic fatigue, which can be observed in various pathological conditions. The article discusses the classification, as well as the features and criteria for diagnosing of asthenic disorders (AD). The close relationship and common pathogenetic mechanisms of the development of asthenia and cognitive impairments (CI) in cerebral diseases are reflected. Issues of management of patients with asthenia and concomitant CI are discussed, which should be comprehensive and include non-drug and drug treatment methods. Non-drug methods, including methods of cognitive stimulation and cognitive training, are coming to the fore in the treatment of various manifestations of AD. The possibilities of therapy with phenylpiracetam for asthenic syndrome of various origins, including those with concomitant anxiety-depressive disorders and CI, have been shown.