The methodology used in an Environment Impact Study of several Mediterranean aquaculture projects is here explained. The impact caused by this activity has been classified into biotic and abiotic pollution. Moreover, the type of project (protected or exposed cages) and the environment are studied. The relevance of the impact on land is consider higher than in marine habitats, where horizontal impacts are taken into account, mormally by setting control stations away from the origin of the disturbance. It is important to differentiate changes caused in the environment from those caused by environmental seasonal variations. Consequently, a previous knowledge of the environment is essential. Regarding methodology, it is suggested to study local currents, with the aim of modelling pollutant dispersion. In this way, we can locate the sampling stations for the Environment Control Program, which aims to check if the predictions are fulfilled, and propose corrective steps, if needed.