It was recalled that, in order to explain the complex results obtained when creep property measurements were described by using power-law equations, it was usually assumed that a transition from dislocation to diffusional creep occurred with decreasing applied stress. However, this assumption was questioned by the results found for aluminium, copper and various particle-hardened alloys. All of the features of power-law behaviour for copper were predicted by new relationships which were based upon normalization of the stress with respect to the yield and ultimate tensile stresses determined from high strain-rate tests performed at the creep temperature. Also, the particle-free zones sometimes found on grain boundaries normal to the tensile axis existed before creep and did not provide any definitive evidence for diffusional creep mechanisms. It was therefore proposed that the predominant dislocation processes differed only in detail as the test duration and temperature increased. The Role of Grain Boundaries in Creep Strain Accumulation. B.Wilshire, M.T.Whittaker: Acta Materialia, 2009, 57[14], 4115-24