The measurement of sustainable development is a goal for better performance of any externality producer, and indicators are one way to evaluate the implementation of practical policy decisions. The tourism industry, like many others, is an important source of income for many groups, but is also a serious potential source of environmental problems. Adoption of the sustainable tourism concept is a possible way to approach these problems. To measure the historical behaviour of the tourism industry in the state of Baja California Sur, Mexico we built a sustainable development tourism index based on multivariable analysis of a 34-indicator data set. The analysis covers the period 1990 to 2000. We found a positive trend in the index, derived from 27 indicators of sustainability and an additional 7 strategic tourist indicators. So far, Baja California Sur has been able to absorb the migration and growth, mainly in Los Cabos area, and the index suggested that the environment is apparently not seriously affected yet. However, BCS society must carefully watch the growth of tourism in subsequent years to avoid negative impacts on nature and residents. The proposed index is a performance parameter for measuring sustainable development in tourism not only in Mexico, but also in other countries with an adequate data base of sustainability indicators.