Better access to primary care results in better patient health, fewer visits to emergency departments, and fewer hospital stays leading to lower health system costs. Therefore, health care policy makers across the country and internationally have focused on improving quality and increasing patient access to primary care in order to achieve these outcomes. In Canada, Ontario has implemented the greatest number of changes to primary care delivery but the models they introduced were focused on two key areas: how physicians are paid and the introduction of multidisciplinary teams. Despite more than doubling spending on primary care between 2006 and 2009 to accommodate these changes, there is only very limited evidence telling us whether they have translated into better health or cost savings. The goal of this project is to study the short, medium, and long term effectiveness of the models that were introduced in Ontario over the last 15 years. We are looking to determine which models resulted in changes to the cost of delivering primary care and the total cost of caring for each patient. Multi-disciplinary teams were introduced in part to offload some of the work done by physicians and give that work to other practitioners, so we will also determine whether family physicians were able to care for more patients because of this. Finally, we will also compare the different models of primary care for health outcomes (mortality) and health service utilization (emergency department visits and hospitalizations). Many other provinces are now considering or piloting reforms similar to the ones introduced in Ontario. The results of this study will help Ontario to plan the future of their primary care, and will help other provinces choose the most cost effective changes to introduce.