Sustainable tourism and ecotourism have now been researched in depth for some years. This paper highlights that researchers still have only a limited understanding of what tourist behaviour can be considered as sustainable, and little consensus about who environment-friendly tourists (EFTs) actually are. This study reviews theoretical and empirical studies by tourism researchers, and explores work done on environment-friendly behaviour in other disciplines. Results indicate that operationalisations of EFTs are inconsistent and, at times, do not ensure that EFTs are actually studied, thus jeopardising the quality of cumulative knowledge on this critical issue. There is little insight into who EFTs are. Suggestions for future work are made, which would develop more reliable and generalisable insights into EFT profiles.