 The Cardiac Care Network of Ontario CCN holds a registry of all patients in the province who have a coronary angiography. The registry has been used to identify gaps in care and to plan health system strategies for high-risk patients. More recently, a pilot trial was conducted in Hamilton by the trial team using data in the registry to send recurrent postal reminders regarding the importance of treatment adherence to patients, their pharmacists, and family physicians. A similar program is underway in Ottawa using automated phone calls with interactive voice response and nurse follow up. These interventions both have the potential to address known determinants of adherence. The CCN, Ministry of Health and Long-Term Care, Health Quality Ontario, and other stakeholders across Ontario are interested in evaluating the comparative effectiveness and costs of these interventions. 