The kinetics of the crystallization of the (NH 4-TPA)-ZSM-5 zeolite in two different systems have been determined as a function of the molar ratio of SiO 2 Al 2O 3 and the nature of the silica source. The influence of organic template molecules and the reactivity of silica sources on the rate of crystallization as well as the phase-purity have been investigated. Pure ZSM-5 zeolite can be isolated after five days. A correlation between the XRD crystallinity of the samples with varying degrees of crystallinity and that estimated from the framework IR spectroscopy, SEM and adsorption of n-hexane is demonstrated. The dependance of the morphology and the size of the zeolite crystals of ZSM-5 on the reactivity of the silica sources, the organic templates and SiO 2 Al 2O 3 ratio are also reported. Investigation has revealed that a different mechanism of nucleation and crystal growth takes place in the two systems, albeit they may be related through the templating or clathrating role of the tetrapropylammonium cation.