Many are the factors indicated by the pertinent literature concerning the causes of deforestation in Brazilian Legal Amazon. From endogenous aspects as the edafo-climatic conditions to aspects related to anthropic action, like the population movements, urban growth, and especially, the independent or induced actions of the different public and private economic agents who have acted in the region, historically configuring the processes of occupation of the land and economic exploitation of the Amazonian region. The objective of this article is to perform a causality test, in the Granger sense, in the main variables suggested as important that explain the deforestation of the Legal Amazon, in the period from 1997 to 2006. The methodology to be used is based on dynamic models for the panel data, developed by Holtz-Eakin et al. (1988) and Arellano-Bond (1991) who developed a causality test based on the seminal article of Granger (1969). Among the main results found is the empirical evidence that there is a bidirectional causality between deforestation and the areas of permanent and temporary cultures, as well as the size of the cattle herd.