BACKGROUND:Oxidative stress is an extremely widespread condition manifested in an increased rate of free-radical processes and accumulation of reactive oxygen species (ROS) in the tissues.It appears in different physiologic states and pathological processes accompanied by stimulation of the sympathetic adrenal system or tissue hypoxia or under stress.However,until now,there is still no clarity on the issue of the significance of oxidative stress in the development of adaptation processes in the organism.OBJECTIVE:In the present work we will review the most recent finding about physiologic role of oxidative stress and its participation in adaptation of an organism to effect of different adverse factors.METHODS:A systematic literature search was performed using the Pubmed search engine.Studies published over past 18 years,i.e.between 1998 and 2015 were considered for review.Followed keywords were used:"oxidative stress," "free radical oxidation," "ROS," "endogenous aldehydes," "adaptation." RESULTS:The article cites arguments supporting the notion that oxidative stress serves as a nonspecific link in the adaptation of the human body to the effects of injurious factors.Oxidative stress exerts regulatory effects by changing the redox state of the cell.Oxidative stress affects on various intracellular proteins containing cysteine residues,e.g.,enzymes,chaperones,and transcription factors,etc.For this reason,the use of antioxidants for the treatment and prophylaxis of a wide range of diseases is not recommended.CONCLUSION:Further investigation is needed in this field.The most attention should be paid to careful experimental verification aimed at quantitative assessment of the ROS level in tissues under oxidative stress,as well as at the study of possibility of enhancing the catabolism of free radical oxidation carbonyl products in order to prevent tissue damage under oxidative stress.