Objectives. The United Nations recently published its most definitive report, calling for greater action on climate change. Historically, however, health technology assessment (HTA) has had a more narrow focus with emphasis on the health of patients and health inequalities. Recently some healthcare decision makers have extended the focus to include the environment, e.g. the Swedish Government is considering a Green Premium for generic drugs, and the UK NHS has CO2 emissions targets. We consider the case for incorporating environmental impacts into HTA, and the associated methodological challenges. Methods. We reviewed healthcare decisions where environmental impacts were considered - a summary will be provided in the paper. We then convened a workshop with key opinion leaders. Results. There are two lines of reasoning for incorporating environmental impacts into HTA: 1) Direct impact: changes in the environment could affect the health of individuals; and 2) Health decision makers’ objectives are broader and are informed by other policy goals, such as the CO2 targets adopted by the NHS in the UK. We also identified two types of methodological challenges for implementation. First, the nascent evidence base is insufficient to support the accurate comparison of the environmental impact of technologies.  Second, uncertainty about how best to incorporate evidence into HTA. The cost-utility analysis approach favoured by many HTA agencies could capture some of the value of environmental impacts – in particular, those that generate health impacts. Both cost-benefit analysis and multi-criteria decision analysis have potential, having both previously been applied to evaluate both health and environmental interventions, though are less familiar to health care decision makers. Conclusion Further work is needed to track decision makers’ demand for evidence on environmental impacts. Robust methods also are needed for capturing and incorporating environmental data as part of HTA as more decision makers begin incorporating environmental impacts.