This book demonstrates how optimization, system engineering and statistics can help to improve health care provision and health systems. It gathers the proceedings of the Fourth International Conference on Health Care Systems Engineering (HCSE 2019), which was held in Montreal, Canada, from May 30 to June 1, 2019. The conference provided an opportunity to discuss operations management issues in health care delivery systems, and allowed scientists and practitioners to exchange their latest ideas, methods and technologies for improving the operation of health care organizations. The event was hosted at the Mother and Child University Hospital CHU Sainte-Justine in Montreal, and each session was co-chaired by a discussant from clinical practice, so as to promote close collaborations with clinicians. The respective chapters cover a broad range of concrete problems that pose challenges for researchers and practitioners alike: hospital drug logistics, operating theatre management, blood donation, home care services, modelling, simulation and process mining, and data mining at patient care and health care organizations. .