The hot compaction of nanocrystalline TiO 2 anatase powders is investigated using dilatometry. The constant rate of heating (CRH) method is applied to determine effective activation energies of the processes involved during sintering. Grain size and doping effects are studied, using dopant cations of different radius and charge: Zn 2+ , Al 3+ , Si 4+ , Nb 5+ . The results are interpreted by a mechanism including superplastic deformation and boundary diffusion. The former is predominant for small particles and low temperature, whereas the latter is more important for larger particles and higher temperature. Dopant effects on densification kinetics are discussed in view of defect chemistry.