As hotel companies seek in good faith to determine and report their carbon footprints, often in response to stakeholder requests, the issue of materiality arises, in which the hotel firm must determine what factors are important to greenhouse emissions and which are negligible in terms of emissions. The guidance from existing sources on this question is complex and can be contradictory. In addition to examining the boundaries of materiality, this report presents a materiality analysis of two sources of hotel greenhouse gases, fugitive coolant emissions and mobile fuels. Based on data from 154 hotels in 25 countries, neither source appears to be material for most hotels, since neither exceeds the commonly used cut-off point of 5 percent of total emissions. While the circumstances of a particular hotel might render one of these sources material, they do not seem to merit the industry’s attention for constant measurement.