Recurrent total or partial upper airway collapse occurring during sleep characterizes obstructive sleep apnea syndrome (OSAS). Although the disease is affecting more than 5% of the general population, it remains largely undiagnosed. The disease is associated with augmented cardiovascular risk, reduction in vigilance and attentional abilities, being responsible for traffic or occupational accidents. There is also glucose metabolism impairment likely to occur during OSA i.e. resistance to insulin and diabetes. Simplified tools are available in order to achieve the diagnosis either in the sleep laboratory environment or ambulatory. Nasal continuous positive airway pressure (CPAP) remains the reference treatment. CPAP acts as a pneumatic splint that maintains UA patency. CPAP efficiency is well demonstrated, both on sleepiness and cardiovascular outcomes. Oral appliance is an alternative to CPAP in sleep apnea syndrome, preferentially when moderate in non-obese subjects. Surgical treatment remains poorly efficient and is of limited use in OSA. Lastly, pharmacological developments are currently being evaluated regarding symptoms such as sleepiness or comorbidities.