Hypoxia is a typical pathological process characterized by oxygen tissue deficiency with the pathological and protective-compensatory reactions. The article briefly outlines the issues of hypoxia study and interval hypoxic training in clinical and rehabilitation practice while treating various diseases and pathological processes. The authors consider types of physiological and pathological responses to hypoxia, key aspects in the pathogenesis of normo- and hypobaric hypoxia under normal and reduced atmospheric pressure, and stages of hypoxia development. Physiological and biochemical responses to interval hypoxic training are associated with oxidative stress, which develops as a result of an imbalance between the pro- and antioxidant systems, and excessive production of reactive oxygen species. Interval hypoxic training is aimed at adequate activation of defense systems with the formation of stable adaptation to damaging factors. The authors prove the key role of HIF-1α biological effects in the mechanisms of cellular and tissue adaptation to oxygen deficiency. The authors also analyze the role of adenosine and adenosine receptors in acute and chronic inflammatory diseases associated with tissue hypoxia.