Aim. The objectiv of the present study was to elucidate correlation between the clinical manifestations of snoring, the obstructive sleep apnea shyndome (OSAS), and the functional characteristics of the upper respiratory tract (URT). Patients and methods. A total of 113 patients presenting with snoring and OSAS were studied with the use of polysomnography (PDG) and sleep endoscopy based at the Scientific and Clinical Center of Otorhinolaryngology, FMBA, during the period from 2015 till 2018.The results of sleep endoscopy were evaluated based on the NOHL and VOTE systems and on the original MRKN estimation system proposed by the authors. Results. The evaluation based on the VOTE system revealed obstruction at the level of the soft palate in 88 patients including 25 ones suffering complete obstruction. The antero-posterior obstruction at the level of the soft palate was documented in 60 patients, the concentric and lateral narrowing in 25 and 3 patients respectively. The obstruction at the level of the oropharynx and the root of the tongue was absent in 68 and 56 patients respectively. Eight patients had total obstruction at the level of the root of the tongue; the partial obstruction at this level was documented in 25 patients. 79 patients had the epiglottic cartilage at the normal level. Six and four patients had total and partial obstruction at this level. The results of the evaluation of the obstruction and the shape of the narrowing at the level of the soft palate based on the MRKN system were virtually identical with those based on the VOTE system. The narrowing at the level of the oropharynx was absent in 68 patients, significant in 15 and insignificant in six patients. 56 patients did not have obstruction at the level of the root of the tongue. Ten patients had insignificant obstruction at this level; it was significant in 23 other patients (including 15 in whom it developed as a result of hypertrophy of the lingual tonsils and 8 ones in whom the obstruction was attributable to lingua muscle hypertrophy). 79 patients had epiglottis at the normal level, eight and two patents had significant and insignificant obstruction at this level, respectively. Conclusion. The results of the present study give evidence of the correlation between the severity of the obstructive sleep apnea shyndome and the level and the shape of the narrowing. The mild form of OSAS is most frequently associated with the isolated antero-posterior obstruction at the level of the soft palate. Moderately severe OSAS is characterized by the combination of the antero-posterior obstruction at the level of the soft palate and partial obstruction at the level of the root of the tongue. The concentric narrowing at the level of the soft palate and the complete obstruction at the level of the root of the tongue is characteristic of the severe obstructive sleep apnea shyndome.