Using quantitative immunohistochemistry, changes in the expression of the BDNF (Brain-Derived Neurotrophic Factor) were studied in the hippocampus and neocortex of 24 male Wistar rats during the development of post-stress-related anxiety state in the experimental model of posttraumatic stress disorder, and its correction by hypoxic postconditioning (PC). For the induction of anxiety state, combined severe psychoemotional stress was applied (immobilization, forced swimming, ether stress followed 7 days later by repeated immobilization - restress). Correction of the anxiety state was achieved by application of hypoxic PC, which included three sessions of mild hypobaric hypoxia (360 mm Hg, 2 h, daily). The formation of the anxiety pathology was accompanied by a significant reduction in the expression of immunoreactive BDNF in dorsal (CA1) and ventral (dentate gyrus) hippocampus and neocortex, while hypoxic PC resulted in partial (hippocampus) or complete (neocortex) restoration of BDNF expression. The results indicate that the neurotrophic factors, and BDNF in particular, seem to play an important role in the pathogenesis of the anxiety-depressive disorders as well as in mechanisms of proadaptive and neuroprotective effects of hypoxic PC.