A detailed study of the kinetics of crystallization of zeolite MEL was carried out at temperatures of 120, 135 and 150 degrees C for time intervals between 0 and 72 h. The evolution of the nucleation and growth process was followed by X-ray powder diffraction, Infrared Spectroscopy and Scanning and Transmission Electron Microscopy. The kinetic of crystallization showed a Kolmogorov-Johnson-Mehl-Avrami (KJMA) type behaviour. The apparent activation energy values for induction and transition between induction and growth were calculated by the Arrhenius equation resulting in values of 58 and 21 kJ/mol, respectively. The initial stages of nucleation and growth showed formation of small globular nuclei which evolve at different crystallization rates to complete crystallization depending on the temperature. The transformations occurring during the crystallization process of zeolite MEL were followed by ex situ characterization techniques. (c) 2005 Elsevier B.V. All rights reserved.