Nanocrystalline powders are expected to exhibit viscous flow during sintering due to presence of substantial amount of quasi-amorphous layers at the grain boundaries. The present investigation attempts to determine the contribution of viscous flow during sintering of nanocrystalline titanium powders. Model equations originally suggested by Frenkel are applied on the shrinkage data to determine the activation energy for viscous flow, frequency factor and the coefficient of viscosity. Nanocrystalline titanium powders were found to exhibit lower activation energy for viscous flow, higher frequency factor and higher coefficient of viscosity as compared to micron sized titanium powders. (C) 2006 Elsevier Ltd. All rights reserved.