IntroductionClimate change as the result of human action and the risks it poses to human health are well established. In healthcare there is increasing attention to climate and environmental impacts of the use of medical and health technologies. As part of a lifecycle approach, health technology assessment (HTA) needs to take climate and environmental impacts into account. In 2020, the new definition of HTA added the dimension ‘environmental aspects’, with which the value of health technologies can be determined and assessed in terms of their impact on the environment. This led several HTA organizations to explore opportunities for including environmental impacts in HTA procedures. It is, however, yet unclear how many researchers and HTA organizations are already working on this sustainability dimension, in what way, with which (international) partners, and what they have achieved as of now. Furthermore, the complex relations between the climate crisis, environmental pollution, health and care are difficult to trace, and methods are scarce. In HTA, there is an increasing need for outcome measures that, in addition to clinical utility, effectiveness, efficiency or satisfaction, also quantify the environmental impact of medical interventions (i.e., green metrics).MethodsWe report on (i) a scoping of international (research) groups and (HTA) organizations that are working on green metrics; (ii) a literature review into the state of affairs with regard to metrics and methods; and (iii) an impact analysis of possible future inclusion of green metrics in HTA procedures. We supplemented a review of (grey) literature with interviews with HTA organizations pioneering with green metrics, and we have conducted a review of available scientific literature, yielding examples of incorporation of environmental aspects into HTA and reports on practical implications.ResultsCarbon dioxide emissions and pollution by the health sector are currently being explored as green metrics. Differences between direct and indirect environmental impacts complicate the evaluation.ConclusionsGreen metrics should eventually make it possible to assess sustainability in healthcare as part of a lifecycle approach.