SyntheaTM is an open-source, synthetic patient generator that models the medical history of synthetic patients. Our mission is to provide high-quality, synthetic, realistic but not real, patient data and associated health records covering every aspect of healthcare. The resulting data is free from cost, privacy, and security restrictions, enabling research with Health IT data that is otherwise legally or practically unavailable. The models used to generate synthetic patients are informed by numerous academic publications. Our synthetic populations provide insight into the validity of this research and encourage future studies in population health. Synthetic data establishes a risk-free environment for Health IT development and experimentation. This includes the evaluation of new treatment models, care management systems, clinical decision support, and more.