Publications on mountaineering and alpinism underline the impact of numerous stress and interfering factors connected with high altitudes. Among different psychopathological syndromes they cause, acute mountain sickness has been relatively best described. Its complications, particularly high-altitude cerebral edema and high-altitude pulmonary edema, may become life-threatening. In the course of acute mountain sickness, various psychopathological symptoms may be observed, among which cognitive and psychotic symptoms have been described in most detail, both in scientific and popular literature. Recently, the significance of anxiety symptoms and sleep disorders has also been indicated. The latter are characteristic for both acute and chronic forms of mountain sickness, which affects indigenous and migrant populations for a long time inhabiting high altitude areas. There are also indications for the existence of distinctive impairments of the central nervous system as a result of long-term exposure to high-altitude mountain environment. The syndrome has been termed high-altitude cerebral asthenia. Its axial symptoms can be divided into intellectual, emotional and impulsive function impairments. The existing studies have provided evidence for distinguishing three forms of highland asthenia: characteropathic, encephalopathic and neuroplegic. This paper discusses the psychopathological picture of chronic mountain sickness and high-altitude cerebral asthenia, based on the current state of research concerning the cognitive functioning of mountaineers.