Obstructive sleep apnea syndrome (OSAS) is a complete or partial airway obstruction that can cause significant physiologic disturbance with various clinical impacts. The etiology is multifactorial and its clinical manifestations are night snoring, headache when patient wakes up, day-time sleepiness and degrease of cognitive performance. Some recent international studies suggest that the OSAS prevalence is 2-4% in men and 1-2% in women of average age. The aim of this work was presenting a literature review in Medline concerning Obstructive sleep apnea syndrome. A review of the articles ranging from 1980 to 2014 has been done. Over 2000 articles were found and those which give useful information about etiology, diagnosis, therapy and found results after the study were selected and evaluated. In literature there is no unanimous opinion on the treatment of OSAS. According to the majority of the authors it should be multidisciplinary. The choice of therapy is predicated on the etiology, severity and natural history of the increased upper airway resistance. The importance of a praecox diagnosis and orthodontic therapy in order to re-establish normal function is underlined, since OSAS is linked with high risk of hypertension, cardiovascular diseases, daytime sleepiness, home and work-related accidents, with consequent worsening of life quality.