A new model for the structural development of extensional basins is outlined. The model suggests a close similarity in geometry between faults in high extension basins such as the North Sea and those in contractional zones. The geometric analogues are discussed and where necessary new terms are introduced to describe the structural style in the context of basin formation. Parallels are noted between contractional and extensional systems in deep crustal control on ramp and flat deformation zones which are now being interpreted from deep reflection work, e.g. MOIST and COCORP. The model is based on interpretation of industry seismic records particularly in the North Sea, and on field analogues of extensional faulting in the Basin and Range province of Nevada.