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. A model development procedure is proposed: identification of the dimensions (economic, socio-ecologic, infrastructure) and indicators, method of scaling, chart representation and evaluation on three Asian countries. This application to three countries show us that a similar level of tourism activity might induce different sort of improvements to implement in the tourism activity and might have different consequences for the socio-ecological environment. The heterogeneity of developing countries exposed in the STBT is useful to detect the main problem of each country in their tourism activity.