Non-surgical treatment of the sleep apnea syndrome comprises behavioral modification such as sleep hygiene, weight reduction, and positional training as an adjunct to standard therapy with continuous positive airway pressure (CPAP) applied via a nasal mask. For patients who cannot tolerate or are not willing to use CPAP for psychological or other reasons, removable intraoral appliances that advance the mandible during sleep are a valuable treatment alternative. Randomised controlled trials have confirmed effectiveness of intraoral appliances in relieving symptoms and measured sleep and respiratory disturbances. Side effects including hypersalivation, mucosal dryness, tooth and temporo-mandibular joint discomfort are common but usually mild. To timely detect effects of oral appliances on occlusion and on the temporo-mandibular joint longterm orthodontic monitoring is advisable.