Authors research clinical medical importance of hypobaric ascends to an attitude of 5000 meters for 20 minutes for detection of latent forms of diseases and assessment of professional health and ascends to an attitude of 5000 and 6000 meters for 5 minutes when performing psychophysiological training for high altitude flying. According to test of 1326 pilots of Russian Air Forces, including pilots with different diseases, hypobaric ascends showed high diagnostic effectiveness for the professional health assessment. By using of both methods it was revealed that frequency of detection of decreased tolerance to hypoxia is the same (in average in 2,7 and 3,1% of total number of patients). By ascends in 38 patients (2,9%) was revealed decreased tolerance to hypoxia of medium level. It indicated about low functional state and space capacity of pilots. It was proved that hypobaric ascends of 5000 and 6000 meters for 5 minutes could be considered as an effective method of checkup of aircrew for the aviation physical examination.