The objective of this research is to develop an Environmental Social Development Index (IDSA) for the counties in the Legal Amazon. As the annual rate of deforestation dropped to low values since 2005 and it is necessary to identify the relationship of environmental policies goals, such as PPCDAm in economic and social variables. We used factor analysis in order to obtain the factor scores and clusters identification to construct the proposed index. The results indicate that around 51.6% of the municipalities in the region are in socio-environmental vulnerability situation, especially those located in the states of Pará, Maranhão and Amazonas. Only 16.8% of the municipalities - the vast majority in the state of Mato Grosso - have high IDSA. The results indicate that local and regional actions should be directed to the poorest areas of the Legal Amazon. Creation of large areas of environmental protection and sustainable use opens the possibility of a new pattern of regional economic exploitation, such as ecosystem services.