In the last two decades, the problems related to the preservation of the environment and the resources of the planet have been dramatically highlighted by different phenomena (thinning of ozone layer, greenhouse effect, decreasing of forests, air pollution, increasing difficulties in the industrial and domestic waste management, etc.). In order to face this situation, the governments have begun to apply rules to control some aspects of the industrial production and energy. Consequently, the environment has become an interesting issue also for the researchers. A key-point in these new techniques, grouped under the name of "sustainable development", is the disassembly and recycling of the end-of-life goods, necessary to minimize the environmental impact of discarded materials and energy consumption. In this keynote paper the state of the art of the software tools developed to help the designer and the dismantler in the optimization of the disassembly-for-recycling of discarded goods is discussed. The architecture of a complete and general computer aided disassembly planning system is described and a number of system developed both in the academic institutes and in the industry are shown together a review and classification of the different adopted solutions.