The kinetics of melt intercalation of poly(propylene)/montmorillonite nanocomposites was studied by a rheological approach. The experimental sample was elaborately prepared to investigate the whole intercalating process. The intercalation process was demonstrated by the changes of the viscoelastic response with annealing time. The development of the relative volume fraction of intercalated tactoids was obtained from the rheological characterization. The apparent diffusivities was determined and the activation energy of melt intercalation was found to be about 80 +/- 6 kJ/mol. (C) 2003 Wiley Periodicals, Inc.