Executive summary: Tourism is often proposed 1) as a strategy to fund conservation efforts to protect great apes and their habitats, 2) as a way for local communities to participate in, and benefit from, conservation activities on behalf of great apes, or 3) as a business. A few very successful sites point to the considerable potential of conservation-based great ape tourism, but it will not be possible to replicate this success everywhere. The number of significant risks to great apes that can arise from tourism reqire a cautious approach. If great ape tourism is not based on sound conservation principles right from the start, the odds are that economic objectives will take precedence, the consequences of which in all likelihood would be damaging to the well-being and eventual survival of the apes, and detrimental to the continued preservation of their habitat. All great ape species and subspecies are classified as Endangered or Critically Endangered on the IUCN Red List of Threatened Species (IUCN 2010), therefore it is imperative that great ape tourism adhere to the best practice guidelines in this document. The guiding principles of best practice in great ape tourism are: Tourism is not a panacea for great ape conservation or revenue generation; Tourism can enhance long-term support for the conservation of great apes and their habitat; Conservation comes first--it must be the primary goal at any great ape site and tourism can be a tool to help fund it; Great ape tourism should only be developed if the anticipated conservation benefits, as identified in impact studies, significantly outweigh the risks; Enhanced conservation investment and action at great ape tourism sites must be sustained in perpetuity; Great ape tourism management must be based on sound and objective science; Benefits and profit for communities adjacent to great ape habitat should be maximised; Profit to private sector partners and others who earn income associated with tourism is also important, but should not be the driving force for great ape tourism development or expansion; Comprehensive understanding of potential impacts must guide tourism development. positive impacts from tourism must be maximised and negative impacts must be avoided or, if inevitable, better understood and mitigated. The ultimate success or failure of great ape tourism can lie in variables that may not be obvious to policymakers who base their decisions primarily on earning revenue for struggling conservation programmes. However, a number of biological, geographical, economic and global factors can affect a site so as to render ape tourism ill-advised or unsustainable. This can be due, for example, to the failure of the tourism market for a particular site to provide revenue sufficient to cover the development and operating costs, or it can result from failure to protect the target great apes from the large number of significant negative aspects inherent in tourism. Either of these failures will have serious consequences for the great ape population. Once apes are habituated to human observers, they are at increased risk from poaching and other forms of conflict with humans. They must be protected in perpetuity even if tourism fails or ceases for any reason. Great ape tourism should not be developed without conducting critical feasibility analyses to ensure there is sufficient potential for success. Strict attention must be paid to the design of the enterprise, its implementation and continual management capacity in a manner that avoids, or at least minimises, the negative impacts of tourism on local communities and on the apes themselves. Monitoring programmes to track costs and impacts, as well as benefits, [is] essential to inform management on how to optimise tourism for conservation benefits. These guidelines have been developed for both existing and potential great ape tourism sites that wish to improve the degree to which their programme constributes to the conservation rather than the exploitation of great apes.