There are ~6,200 children in Ontario with special and complex healthcare needs requiring multiple services from many different doctors and other healthcare providers. These children are at a high risk of missed, duplicated or inappropriate care, and extraordinary financial burden and stress on families. While small in number (<1% of Ontario kids), these children use 1/3 of all child healthcare resources, and are known to desperately need coordinated care to optimize their health. Complex Care Kids Ontario (CCKO) brings together researchers, children and families, and healthcare providers from across Ontario to develop, implement and evaluate an evidence-based and coordinated model of care for every child with medical complexity in Ontario.