This book presents the proceedings of the Fourth International Conference on Health Care Systems Engineering (HCSE 2019), which took place in Montreal, Canada, from May 30 to June 1, 2019. The event took place in the mother and child university hospital CHU Sainte-Justine in Montréal, and each session was co-chaired by a discussant coming from the clinical practice. The conference offered scientists and practitioners an opportunity to discuss operations management issues in health care delivery systems, and to share new ideas, methods and technologies for improving the operation of health care organizations. Focusing on applications of systems engineering, optimization and statistics to improve health care delivery and health systems, the book covers topics relating to a broad spectrum of concrete problems that pose challenges for researchers and practitioners alike, including hospital drug logistics, operating theatre management, blood donation, home care services,modeling, simulation, process mining and data mining in patient care and health care organizations.