In our past work on target populations, we have measured the cost burden of chronic disease and highlighted the cost burden of mental health conditions in the health system. In our measurement of performance across Health Links we have uncovered the importance of socio-economic factors in determining health system performance in Ontario. This highlights the need to ensure we address equity and population health across all of the work that we undertake. Advancing health system performance requires that the needs among different kinds of high cost users be addressed by effective interventions that are targeted appropriately and implemented rigorously. We aim to better understand, characterize and predict high cost and complex patient populations to inform the implementation and targeting of effective interventions to address the needs of specific patient groups. We engage with patients in patient-centered qualitative research to understand the patient experience and needs among high cost patients with complex care needs. We undertake empirical patient-centered analyses, tracking patient trajectories of care using rich health administrative and health survey data in Ontario. These include projects with a population health emphasis, projects focused on development of patient-centered episodes of care, projects aimed to better understand the complexity of mental health and physical chronic conditions.