A new law in Ontario, called the Patients First Act, requires public health units (PHUs) and Local Health Integration Networks (LHINs) to work together in new ways. This project aims to answer the question, “What are the key elements for a successful collaboration between LHINs and PHUs as required by Patients First legislation, to improve the health system in Ontario informed by a population health approach?” We know that not all PHU and LHIN relationships are the same. We will make a special effort to engage key groups throughout the project to learn from collaboration already in progress in Ontario. The project team will gather information to: - learn what PHUs and LHINs expect of and offer each other for shared population health work. - determine what information can best support health system planning and delivery and whether this information takes into account all the factors that influence health over lifetimes.