Given the complexity of the issues surrounding the concept of sustainable tourism, the current paper tries to provide a unified methodology to assess tourism sustainability, based on a number of quantitative indicators. The proposed methodological framework (Sustainable Tourism Benchmarking Tool ? STBT) will provide a number of benchmarks against which the sustainability of tourism activities in various countries can be assessed. The methodology used includes the following steps: identification of the dimensions (economic, socio-ecologic, infrastructure) and indicators, method of scaling, and chart representation. To illustrate the usefulness of the STBT, tourism sustainability is assessed in Indonesia, Malaysia and Thailand. The preliminary results show that a similar level of tourism activity across countries might induce different economic benefits and might have different consequences for the socio-ecological environment. Therefore, the STBT is a useful tool to assess the heterogeneity of developing countries and detect the main problems each country faces in their tourism development strategy.