Although positive airway pressure is the most efficacious treatment for obstructive sleep apnea (OSA), its clinical effectiveness is limited by its obtrusive interface. Two alternative treatment modalities used in clinical practice are mandibular advancement devices (MADs) and positional therapy. The goals in treatment of OSA are to prevent obstructive apneas and hypopneas, to improve symptoms, and to modify the increased cardiovascular risk. MADs achieve this by mechanically protruding the mandible, thereby increasing the dimensions of the upper airway and reducing its collapsibility. By avoiding supine sleep, positional therapy improves the patency of the upper airway in those with positional OSA. There is now a relatively strong evidence base to support the use of MADs in clinical practice, with research studies assessing the impact of treatment on a range of health outcomes. The revised clinical practice parameters of the American Academy of Sleep Medicine recommend their use for mild to moderate OSA; or for patients with severe OSA who are unable to tolerate or refuse treatment with positive airway pressure. The evidence base for positional therapy is emerging, but is less well developed. A better understanding of the range of OSA phenotypes and predictors of response to different treatment modalities is required to allow physicians to tailor the choice of treatment to the individual patient.