Annual revenue flow to developing countries for ecotourism (or nature-based tourism) could be as large as US$ 210×1012, providing an enormous financial incentive against habitat loss and exploitation. However, is ecotourism the most privately and/or socially valuable use of rainforest land? The question is rarely answered because the relevant data, estimates of profits and fixed costs, are rarely available. We present a social cost-benefit analysis of land use in an ecotourism cluster in the Tambopata region of Amazonian Peru. The net present value of ecotourism-controlled land is given by the producer surplus (profits plus fixed costs of ecotourism lodges): US$ 1,158 ha?1, which is higher than all currently practiced alternatives, including unsustainable logging, ranching, and agriculture.