Aim. To perform a dynamic study of Β-endorphin, hypoxia-inducible factor-1α (HIF-1α), and cytokines in hematologic patients. Subjects and methods. Fifty-nine patients with different types of acute leukemia (AL), 30 with anaplastic anemia (AA), 24 with thrombocytopenic purpura, and 20 healthy volunteers were examined during their 40-day stay at 3200 m above sea level. Β-Endorphin and HIF-1α were measured by a sandwich-type enzyme immunoassay using the Abcam antibodies. Cytokines (interleukin (IL)-2, IL-6, and tumor necrosis factor-α) were estimated by enzyme immunoassay applying the Pro Con kits (Saint Petersburg). Results. Serum Β-endorphin concentrations were 1.5-2-fold above the normal values in the majority of patients with AL. The patients with initial leukocytosis at onset of disease were noted to have elevated white blood cell Β-endorphin concentrations up to 85.9±22.4 pg/ml; moreover, during chemotherapy this index increased about two times (170.74±33.8 pg/ml). There was a direct correlation between the concentrations of Β-endorphin and HIF-1α (r = 0.9) and an inverse correlation between the levels of IL-6 and Β-endorphin (r = -0.7). On ascending to 3200 m, under the conditions of hypoxic hypoxia the patients with AA or idiopathic thrombocytopenic purpura showed a considerable increase in serum Β-endorphin concentrations, mainly in the acute period of being at high altitudes. Conclusion. Stress factors (tumor, use of cytostatics, pain, anemia, hypoxia, high environment temperature) stimulate the elaboration of Β-endorphin, particularly in the white blood cells of patients with AL during chemotherapy. The highest elevation in the index was seen during acute adaptation to hypoxic hypoxia.