In this study the fabrication of a simplified mandibular advancement device for sleep apnea syndrome was described. Its effect on respiratory function and sleep quality variables was evaluated polysomnographically in 256 patients with sleep apnea syndrome and snoring. Polysomnographic recordings were performed twice, before and after insertion of the oral appliance. The mean apneahypopnea index (AHI) decreased significantly (p < 0.0001) with the appliance to 18.2 from 43.2 without it. Responders defined by AHI < 10 were 54% and those defined as a 50% decrease of AHI were 66%. Oxygen saturation, duration of apnea, sleep efficiency, and total arousal were improved significantly after treatment without major side effects. The device improved significantly the respiratory function and sleep quality in patients with sleep apnea syndrome. Compliance was about 90% followed for 2.5 years. This appliance offers some advantages over other therapies because it is noninvasive, easy to fabricate, and well accepted by patients.