The diffusive transport of chromium in both pure and Y-doped fine-grained alumina has been investigated over the temperature range 1250 degrees-1650 degrees C. From a quantitative assessment of the chromium diffusion profile in alumina, as obtained from electron microprobe analysis, it was found that yttrium doping retards cation diffusion in the grain-boundary regime by over an order of magnitude. The Arrhenius equations for the undoped and Y-doped samples were determined to be: delta D-b=(4.77 +/- 0.24) x 10(-7) exp (-264.78 +/-47.68 (kJ/mol)/RT)(cm(3)/s) and delta D-b=(6.87 +/- 0.18) x 10(-8) exp (-284.91 +/- 42.57 (kJ/mol)/RT)(cm(3)/s), respectively. Finally, to elucidate the mechanism for this retardation, the impact of yttrium doping on diffusion activation energies and prefactors was examined.