This collection of 27 review and research papers provides an overview of the geodynamic concepts of channel flow and ductile extrusion in continental collision zones. The focal point for this volume is the proposal that the middle or lower crust acts as a ductile, partially molten channel flowing out from beneath areas of over-thickened crust, such as the Tibetan plateau, towards the topographic surface at plateau margins. This controversial proposal explains many features related to the geodynamic evolution of the plateau and, for example, extrusion and exhumation of the crystalline core of the Himalayan mountain chain to the south. In this volume thermal-mechanical models for channel flow, extrusion and exhumation are presented, and geological and geophysical evidence both for and against the applicability of such models to the Himalayan-Tibetan Plateau system, as well as older continental collision zones such as the Hellenides, the Appalachians and the Canadian Cordillera, are discussed.