Adherence to continuous positive airway pressure (CPAP) treatment for obstructive sleep apnoea (OSA) is a critical problem. Poor adherence (30-60%) to CPAP is widely recognized as a significant limiting factor in treating OSA, reducing the overall effectiveness of the treatment and leaving many OSA patients at heightened risk for co-morbid conditions, impaired function and quality of life. The extant literature examining adherence to CPAP provides critical insight to measuring adherence outcomes, defining optimal adherence levels, and predicting CPAP adherence. This research has revealed salient factors that are associated with or predict CPAP adherence and may guide the development of interventions to promote CPAP adherence. Over the past 10 years, intervention studies to promote CPAP adherence have incorporated a multitude of strategies including education, support, cognitive behavioural approaches, and mixed strategies. This review of the current status of research on CPAP adherence will (i) synthesize the extant literature with regard to measuring, defining, and predicting CPAP adherence; (ii) review published intervention studies aimed at promoting CPAP adherence; and (iii) suggest directions for future empiric study of adherence to CPAP that will have implications for translational science. Our current understanding of CPAP adherence suggests that adherence is a multi-factorial, complex clinical problem that requires similarly designed approaches to effectively address poor CPAP adherence in the OSA population.