Obstructive sleep apnea (OSA) is a prevalent condition causing unrefreshing sleep and excessive daytime sleepiness. It has individual socioeconomic impacts and, through association with increased risk of road traffic accidents, diabetes, and cardiovascular disease, OSA is a public health issue. Continuous positive airway pressure (CPAP) is the first-line treatment for moderate-to-severe OSA. It is effective in improving excessive daytime sleepiness and quality of life. There is also evidence that CPAP therapy has cardiovascular benefits although nature and extent remain uncertain. Despite its benefits, a significant proportion of patients are unable to tolerate CPAP. There are also patients with mild but symptomatic disease, for whom CPAP is usually not available or appropriate, so there is a need for other treatment options. Mandibular advancement devices (MADs) offer an effective alternative to CPAP and can improve daytime symptoms and quality of life. There are many devices available, representing a range of complexity and cost. It is challenging to properly evaluate the effectiveness of this ever-evolving range. The more basic MADs are cheaper and more accessible but are less well tolerated. More complex devices are better tolerated and may be more effective. However, they are more expensive and often require dental expertise, so access is more limited. Efforts continue to try to improve accessibility to effective MAD therapy. Alongside increasing awareness, this may be facilitated by developing and refining devices that could be fitted by non-dental clinicians, and potentially by patients themselves. Research efforts need to focus on determining how to efficiently identify patients who are likely to respond to MAD therapy, so as to improve clinical and cost-effectiveness of OSA therapy overall.