The paper begins to define a framework for analysing and addressing the health sector's climate footprint — including identifying seven aspects of a climate-friendly hospital. It also draws on a series of examples from around the world that demonstrate that the health sector is indeed already beginning to provide leadership in this most important area of concern to the global community. This paper is the first step in a WHO project in collaboration with Health Care Without Harm (HCWH) aimed at addressing the climate footprint of the health sector.