Analysis of environmental problems is complex and requires a large quantity of data. We have developed a decision-making assistance tool for evaluating and reducing pollution (Nitrogen and Phosphorous) from intensive rearing facilities. This was possible thanks to computer technology : the A.I.S.O.E. (Agricultural Information System Oriented Environment) has been designed to integrate the various levels requiring consideration (region, farm, plot). This method allows the system to be progressive ; the modular design means that different application programmes can be developed to operate at the various geographical levels. For example, this tool allows identification of critical non point-pollutant contributing aeras in Brittany and will be useful for targeting further investigations and control programs.