Abstract : Tourism is a significant resource for Tunisia. Its economic impacts on the country are considerable (6% of GDP and over 386 000 direct and indirect jobs in 2009). But today, the tourism sector is facing many difficulties. This thesis is part of a plan to boost tourism in Tunisia. It is structured in two parts. The first diagnosis of the Tunisian tourism sector shows that it suffers on two levels: strategic (management is left to the private sector without government intervention, which leads to low profitability of some hotels, a high debt because of the pricing practice and the family business model) and qualitative (over-reliance on the Fordist model). The thesis discusses the limitations of Fordism quantitative, and demonstrates that a new reading of the tourism market is needed to achieve sustainable economic performance. From this perspective, the implementation of economic and environmental assessments is required. In the second part on the thesis, envisions a new trajectory for a specific territory (Djerba Island), it is to think of new trajectories. The work demands the search of relevant indicators of economic and environmental quality in order to assess the best methodologies to improve the assessment of the profitability of the tourism sector. Economically, the study proposes a new method for assessing the economic impact of tourism on the island of Djerba. This method called "method of the masses", builds on the theory of growth or development. It requires the determination of direct, indirect and induced activities. The indicators measured are: Value Added (VA), Earnings Before Interests, Taxes, Depreciation and Amortization (EBITDA) and Employment (E). The results show that the most direct activities that generate wealth and jobs are hotels. For indirect activities, it is the consumption of food products, agricultural products and fisheries. These results may provide a basis upon which for policy-makers may evaluate future tourism development projects. In terms of assessing the importance of the environment, it allows the Djerbian tourism to defend its future. This evaluation will also examine the environmental dimension and provides an analysis of regulatory instruments in place in Djerba and seeks to integrate new instruments proposed by the World Tourism Organization which objective is to search for sustainable development of tourism activity to conserve the natural wealth of the island.