Various definitions of ecotourism exist in the literature. The definition of ecotourism is important for determining the boundary of the ecotourism industry and its economic value. However, the extent to which ecotourism can be separated from tourism generally or the extent to which a separate tourism industry can be identified is uncertain. Considerable fuzziness exists at the boundaries. Some authors use the term nature-tourism and ecotourism interchangeably, while some limit it to tourism based primarily on living natural things. In principle, the size of the ecotourism industry might be determined from the supply-side e.g. from the specialisation of tourist organisations the extent to which they perceive they are involved in ecotourism, or from the demand-side e.g. the extent to which tourists are involved in or demand ecotourism experiences. These alternative .approaches and the difficulties to be overcome are discussed. • For the purpose of this article, we propose to define ecotourism as a kind of tourism which is based on relatively undisturbed living natural areas and at the same time takes particular care of and contributes to the protection of the resources used. Some special features of ecotourism make it a distinctive subset of tourism. The framework for ecotourism study covers the interrelationship between ecotourism and its resources, which are comprised of natural, social, cultural and economic systems. The coexistence of ecotourism and the resources is rooted in the fact that ecotourism depends heavily on the well-protected environment while provides incentives for the continuous conservation of its resource basis. But the natural conflicts must be taken seriously in that the natural condition and variations in the resources have crucial effects on ecotourism, and ecotourism undoubtedly performs as a powerful factor to bring about both favourable and unfavourable changes to its resources. Outlines for a careful cost-benefit analysis of ecotourism are discussed. Planning plays a crucial role to bridge the natural gap between .ecotourism and its resources. Three levels of planning - normative, strategic and operational are best achieved by multi-channel communication among the clients, decision makers, planners and other interested parties. The goal of planning is to ensure the harmonious balance and a sustained ecotourism. Monetary gain from ecotourism can be a misleading criterion for measuring the economic benefit of ecotourism, and could furthermore lead to deprivation of its resources. It is important to make ecotourism financially viable but not at the price of damaging the background on which it depends. As the immediate beneficiary or victim of ecotourism, local communities are closely affected by the long term development of ecotourism. Successes and failures are analysed, and a checklist for community involvement included. Some of the economic problems involved in developing an ecotourism industry are discussed along with the economics of operating ecotourism enterprises. The latter issue has been relatively neglected. Examples of the issues involved are given mainly from China.