Change detection refers to the process of highlighting and placing the alterations of the state of a scene's surface, having been observed in several images. These alterations, or changes, can be: - Slow and tenuous, such as the evolution of the rotations in agriculture or depletion areas. In this case, it is necessary to have a time series of images to detect these evolutions, - Spectacular and fast, such as earthquakes, the damages due to a natural or man- made disasters. Two images acquired before and after the event can be enough to detect them. This type of change is generally qualified as abrupt, which does not mean it is of a large scale, but rather that it is instantaneously sudden. With this chapter, we aim therefore to describe and characterize techniques allowing us to detect these changes. We are not concerned with estimating evolutions parameters (the elevation measures are mainly approached in Chapter 9, and the moving measurements are described in Chapter 10).