The motion of planar symmetrical, <112>- and <111>, tilt boundaries under the influence of a mechanical shear stress was investigated and compared with experiments on curved symmetrical, <112>- and <111>, tilt boundaries having the same angles of misorientation; all under the influence of a constant capillary force. It was found that motion of planar low-angle grain boundaries, as well as planar high-angle boundaries, could be induced by the imposed external stress and that the dependence of the activation enthalpies for grain-boundary motion upon misorientation angle was different for planar and curved <111> grain boundaries. The different observed activation enthalpies were attributed to differing migration mechanisms for grain-boundary motion. It appeared that the activation of a migration mechanism depended upon the misorientation angle and the driving force, and that grain boundaries had the possibility of moving by various migration mechanisms. Regardless of whether the grain boundaries were planar or curved, there was a distinct transition between low-angle and high-angle grain boundaries at the same misorientation angle.On the Mechanisms of Grain Boundary Migration. M.Winning, G.Gottstein, L.S.Shvindlerman: Acta Materialia, 2002, 50[2], 353-63