The Antarctic Peninsula Mesozoic magmatic arc has had a long history of dextral, strike-slip deformation. The deformation was initially associated with the development of a wide accretionary complex, by the migration of fore-arc slivers, and the formation and inversion of a thick fore-arc basin succession. It also formed an important component within major shear zones in the arc, and may have controlled the formation of sedimentary basins in the back-arc region. Although some transcurrent motion within the fore-arc region was related to a component of oblique subduction, the main movement occurred during the breakup of Gondwanaland and the formation of a major transtensional rift system. A new reconstruction for this part of Gondwanaland is presented taking this transcurrent motion into consideration.