How can a concept that individually we believe that we understand, and that is defined as the fastest growing segment of the tourism industry, continue to defy firm definition? While tourists increasingly define themselves as 'eco'–tourists, and the industry operators increasingly posit to offer eco-tours, eco-treks, eco-lodges … ; larger questions remain unanswered: how might we distinguish eco-tourism from other forms of tourism; how do we know when we have achieved eco-tourism; is eco-tourism (of all, or any, other forms of tourism) sustainable? This paper argues that answers to these questions and a more robust definition of ecotourism will be found in better analysis and understanding of eco-tourism practices with the environmental resource bases on which it fundamentally depends.