Background: The aim was to compare ventilatory and heart rate chemosensitivity to hypoxia and hypercapnia in homogenous groups of high performance alpinists and endurance athletes and its relation to special work endurance. Material/Methods: Thirty-two male best national alpinists (30.7±2.7 yrs, VO2max 63.7±1.9 ml. kg-1,min-1, 14.3±2.4 yrs of experience) and 24 high performance male road cyclists of national team (25.7±1.1 yrs, VO2max 74.5±1.5 ml.kg-1,min-1, 11.2±1.4 yrs of experience) were examined by isocapnic progressive hypoxia and CO2 rebreathing tests. Maximal oxygen uptake, lung ventilation and heart rate peak responses were measured in an incremental ergometric test at sea level. Special work capacity of 23 alpinists was evaluated as the best time of non complicated mountain climbing between the point at 3,290 and 4,300 m above the sea level. Special work capacity of cyclists was evaluated as the best time of the individual 50 km race at the sea level. Results: The results showed no significant differences of the hypoxic ventilatory response in groups of alpinists and cyclists (p<0.05) But circulatory response evaluated by response of HR increase in answer to a decrease in O2 arterial blood saturation (SaO2) in alpinists was lower (p<0.05). Results showed that the evaluation of ventilatory and heart rate chemosensitivity in addition to measure of aerobic power may give important information for prevision of specific working capacity of high performance alpinists. Maximal oxygen uptake (ml/kg body mass) of the four best alpinists did not differ from the values of other alpinists. Special work capacity of alpinists was significantly related to tidal volume increase for the hypoxia test (r=-0.60) and to CO2 sensitivity (r=-0.67). Conclusions: The long-term exposure to environmental hypoxia and hypocapnia in alpinists generates specific changes in respiratory control. To evaluate special work capacity potential possibilities in a homogenous group of high performance alpinists first of all heart rate response sensitivity to hypoxia as well ventilatory response sensitivity to CO2had to be taken into account, but only an alpinist's aerobic power.