This is an overview for the non-specialist of the pathophysiology, workup and treatment of the obstructive sleep apnea syndrome. The mechanisms leading to upper airway closure during sleep are discussed, as well as the current theoretical and experimental concepts for the apnea-induced arousal response and the consequent changes in sleep architecture and quality. Epidemiological data are summarized, with special reference to the problems of non-uniform definition criteria and examination techniques applied. In conclusion, a practical workup strategy and the current treatment options are summarized.