Flash-crystallization is a suspension crystallization process to produce small, fine crystals (L-50,L-3= 20-90 mu m) of substances which are well soluble. A hot and undersaturated solution is atomized into a low vacuum. The small droplets generated partially evaporate and cool down until thermal and mechanical equilibrium is reached. Consequently, they are highly supersaturated in a controlled manner and, thus, enable high nucleation rates. Experiments show that only certain solute-solvent combinations exhibit the high nucleation rates required and, thus, are suitable for flash-crystallization. We show that this observation is not caused solely by the buildup rate of supersaturation, but also by nucleation and growth kinetics. This is concluded by a comparison between the time of flight tau(f), of the droplets in the crystallizer And the buildup time tau(b) needed for the evolution of temperature and concentration profiles inside each droplet. The buildup time of supersaturation tau(b) is negligibly short compared to the time of flight of the droplet. Thus, the driving force for nucleation and growth rate is present during virtually the entire time of flight, and therefore, slow nucleation and growth kinetics are the reason for the behavior observed. The model proposed is in good agreement with data measured. (c) 2015 Elsevier B.V. All rights reserved.