Dietary supplement Antihot® was tested as a potential means for increasing human working capacity in a high altitude environment. During three days the volunteers (athletes specializing in mountaineering) climbed to the height of 3,700 m above sea level by marches of 15 km each with a load of 35-40 kg. Twenty nine young men aged 20-35 years old participated in the trip, and 15 of them were taking Antihot® in capsules, 1 capsule (0.5 g) three times a day during a meal, for 4 days. The other 13 men, who were included in the control group, were taking a placebo under a similar routine. Besides hypoxic hypoxia the ascent was complicated by the night temperature fall to -5 °C, preventing the climbers from having rest and recreation. It was registered that with taking Antihot® the climbing was easier to tolerate. The number of complaints recorded in a mountain experience questionnaire decreased, and, above all, the course of halt recreation had run much quicker. In the upland environment, the improvement of a feeling of health was recorded, physical loads got easier to overcome, and fatigue was lowered. A distinct decrease of hypoxic hypoxia was registered. Symptomatology relevant to the presentations of acute mountain pathology developed to a minor ratio and virtually did not affect on the volunteers' functional condition and their marking capacity. In comparison to the control group the average number of complaints decreased to 4 times less, including cerebral and common complaints which decreased by 6 times less, cardiorespiratory ones - to 2.5 times less, and digestive and excretory complaints - 20 times less. These results are sure to argue for distinct antihypoxic action by Antihot®. Heart rate is a general parameter of physiological function tension. At the post-ascent examination of the climbers who had taken Antihot®, it remained lower than background meaning both at rest and while conducting a loading test by 5.5 and 11.4%, respectively. In aggregate with a reliable increase of breath-holding (Stange test) by 25.5% against taking Antihot®, results argue for a favorable preparation impact on the functions of the oxygen transportation system, rapid and complete removal of oxygen debt and, maybe, as a whole, for a decrease of tension level in the body's physiological systems, thus, facilitating adaptation and working capacity in a high altitude environment. Therefore, Antihot® has displayed high efficacy in increasing tolerance to unfavorable factors of environment in high altitude as well as in facilitating tolerance to physical loading and maintaining a feeling of well-being during the whole stay in the mountains. [ABSTRACT FROM AUTHOR]