Non-adherence to evidence-based medications is a major public health problem. Less than 50 % of patients with coronary artery disease adhere to their prescribed therapies and this has important implications for morbidity, mortality, and health care spending. Like most complex behaviors, medication non-adherence is not solely the result of poor patient choices. Rather, there are myriad potential contributors attributable to patients, health care providers, and, more broadly, the health care system. Interventions including patient education and behavioral modification, improving patient-physician communication, and eliminating copayments for preventive pharmacotherapy have all been studied. Clinicians play a critical role in helping improve adherence and assessment of adherence must become a standard component of each clinical encounter. Ultimately, given the various etiologies that contribute to non-adherence, achieving meaningful gains will undoubtedly require payors, providers, and policymakers to develop, rigorously evaluate, and systematically deploy strategies that address key patient, clinician, and health system factors.