As countries face financing constraints in achieving their universal health coverage goals, they must ensure that available resources are spent more efficiently. The institutionalization of health technology assessment mechanisms is one approach to ensuring that decisions on allocating scarce health funds are informed by evidence. This guidance note was prepared for countries that have already made the decision that they require a health technology assessment (HTA) mechanism. It is not intended to convince readers that an HTA is necessary, as it is expected that they have already reached that conclusion. It is designed to be extremely practical, with checklists to support implementation in each chapter. Annotated reading lists are provided for further conceptual understanding.