Since the origin of technology assessment (TA) in the 1960s, including TAs of certain medical interventions, and formal recognition and institutionalization of health technology assessment (HTA) in the 1970s, the field of HTA has evolved in programs large and small in the public and private sectors. It has diffused into an increasing number of nations in a range of policy-making and decision-support contexts. Since its inception, the development and diffusion of HTA have been strongly characterized by international collaboration involving sharing of expertise and practical experience, and joint efforts to advance the state of the art. Also during that time, there have been periodic collaborations to identify or develop standard frameworks, good practices, guiding principles, checklists, and other normative, “how-to” documentation for the field. Recognizing the diversity and ongoing evolution of HTA, these efforts have generally sought to balance the appeal of standardization with that of flexibility to accommodate the ranges of HTA program remits and contexts.