The Cretaceous tectonics of the South American Andes region is the subject of this monograph written by contributors in the field of geosciences worldwide. The theme is not only of interest from an academic point of view given the vast array of tectonic processes which governed the evolution of the Andes towards the end of the Mesozoic. It is also because of the economic importance conferred on this portion of the Earth's crust by the hydrocarbon, uranium and other metallic and non-metallic ore resources contained in its sedimentary and eruptive units.