The periodic congestion and decongestion of the nasal venous sinuses and an alternation of airflow from one side of the nose to the other are known in literature as “nasal cycle”. It is established that nasal cycle during 24-hours registration contains from 4 to 8 time full periods, length of which varies from 0.80 h to 5.75 h. The mean length of all full periods is 2.80 ± 0.17 h. The mean length of full periods of left nostril is 3.07 h and the mean length of periods of right nostril is 2.43 h. The result suggests that there is any asymmetry in length of periods of airflow trough left and right nostrils about 40 min. The longer periods of left nostril can be connected with higher metabolic and functional activity of brain and human organism during active work.