Tourism is now one of the world?s largest industries and one of its fastest growing economic sectors. For many countries tourism is seen as a main instrument for regional development, as it stimulates new economic activities. Tourism may have a positive economic impact on the balance of payments, on employment, on gross income and production, but it may also have negative effects, particularly on the environment. Unplanned and uncontrolled tourism growth can result in such a deterioration of the environment that tourist growth can be compromised. The environment, being the major source of tourist product, should therefore be protected in order to have further growth of tourism and economic development in the future. This is specially true with regard to tourism based on the natural environment as well as on historical-cultural heritage. Sustainable tourism has three interconnected aspects: environmental, socio-cultural, and economic. Sustainability implies permanence, so sustainable tourism includes optimum use of resources, including biological diversity; minimization of ecological, cultural and social impacts; and maximization of benefits for conservation and local communities. It also refers to the management structures that are needed to achieve this. The paper provides a theoretical framework for sustainable tourism. It comprises two parts. The first part presents general views on tourism and sustainable economic development, and some opinions on the relationship between tourism and the environment. The second part concentrates on strategies and policy instruments.