Preliminary data concerning the monitoring in situ of the zeolite A crystallisation from clear solutions are reported. Experiments were performed at 60 and 70 degrees C with fresh and aged solutions having the following composition: 8.6Na(2)O0.18SiO(2)Al(2)O(3). 150H(2)O. The formation of early phases in the crystallisation process were followed using diagnostics such as dynamic light scattering (DLS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The comparison of the available data seems to indicate the formation of a precursor phase (like gel) in the case of not aged solution. Conversely, crystallisation in aged solution seems to proceed without intermediate phases. At the same time, an investigation on the kinetics aspects of the zeolite A crystallisation was carried out. As far as the reproducibility test is concerned, the chemical system selected showed good results on a large number of tests.