At an international level, the implementation of environmental management practices in military facilities is now a growing reality, particularly with the implementation of environmental management programmes and/or systems. The main goal of this research was to assess the Portuguese military sector's environmental performance through an index – the MEPE index – in a simplified and useful manner. A second goal was to measure the units' self-assessment against the environmental profile of the military sector as evaluated through the index, to determine how far they match. The index was deeloped on the basis of the data obtained in a national questionnaire, which was carried out to evaluate environmental practices adopted by military units. Results show that the Portuguese military's overall environmental performance is poor, reflecting that this is quite a new issue in military organizations. Among the military branches the Air Force reveals the best environmental results. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment.