The electronic Child Health Network (eCHN) is an advanced implementation of an electronic health record (EHR). This is a case study of the building of an integrated and shared EHR from multiple systems at multiple sites for the benefit of patients and clinicians. Optimal patient care requires that information about a person's overall health and interactions with the health care system be available to the appropriate providers when and where it is needed. eCHN is a pioneering response to the need for such shared records. A key to its success is that it is a flexible, scalable, open, multi-vendor solution designed to work with existing hospital systems and other networks. As Canada's largest functioning integrated EHR, eCHN is serving three million people and transforming the quality of health record keeping and clinical decision-making. eCHN enables health care providers across Ontario to share accurate patient data – in real time.