The self-diffusivity of 54Mn in single grain icosahedral Al70Pd21.5Mn8.5 quasicrystals has been determined by a precision grinding technique. In the range from 870 to 1093 K the temperature dependence of the Mn self-diffusivity D follows the Arrhenius equation with an activation energy Q = (180.8±4.6)kJmol-1 and a pre-exponential factor D0 = 3.4×10-4m2s-1. The experimental results are discussed together with diffusion mechanisms proposed for quasicrystals from theoretical considerations.