In Morocco, as in several regions of the world, field instabilities are one of the most serious problems on several levels: social, economic and environmental. This study is aimed at the safety of people, the protection of infrastructures and the environment, and on the other hand the forecasting of areas to be avoided for future development. Landslides are polygenic sets that result from the combined action of complex factors. Some, permanent factors, create the essential conditions for instabilities; the others, called dynamic factors, act under the dependence of the former and play the role of detonator. The geological complexity of the land concerned, the diagnosis of the phenomenon is sometime delicate. Risk prevention and protection of populations require, at least for the most threatening sites, delicate and costly studies and recognitions. To stabilize and delineate the damage, several solutions have been proposed and based on the use of various techniques. On the other hand, the preparation of a guide of the stabilization to reinforce the unstable areas has a paramount importance for the development of the regions, which are subjected to rapid and often disorderly urban growth.