This book provides a robust set of health economic principles and methods to inform societal decisions in relation to research, reimbursement and regulation (pricing and monitoring of performance in practice). We provide a theoretical and practical framework that navigates to avoid common biases and suboptimal outcomes observed in recent and current practice of health economic analysis, as opposed to claiming to be comprehensive in covering all methods. Our aim is to facilitate efficient health system decision making processes in research, reimbursement and regulation, which promote constrained optimisation of community outcomes from a societal perspective given resource constraints, available technology and processes of technology assessment. Importantly, this includes identifying an efficient process to maximize the potential that arises from research and pricing in relation to existing technology under uncertainty, given current evidence and associated opportunity costs of investment. Principles and methods are identified and illustrated across health promotion, prevention and palliative care settings as well as treatment settings. Health policy implications are also highlighted.