Mandibular advancement device (MAD) represents a therapeutic option for simple snoring to obstructive sleep apnea syndrome (OSAS). The different available studies report an improvement either on nocturnal respiratory events or on the quality of sleep. The decrease in the intensity of snoring is confirmed by the patient's partner and by objective studies. For the time being the effects of these mandibular advancement devices on the upper airway resistance syndrome has not yet been well documented. The significant clinical improvement is secondary to the decrease in apnea hypopnea index (AHI). A polysomnographically proved cure has been reported with AHI < 10/h. Sleep architecture is also improved with wearing MAD demonstrating a decrease in the time passed in stage 1 sleep and an increase in slow wave sleep and rapid eye movement sleep (REM). A decrease in microarousals index has been shown. Daytime vigilance disorders are subjectively and objectively less remarkable. Then MAD can be beneficial for mild to moderate SAOS.