The kinetics of ZnO nanoparticles was examined by fluorescence measurements. Emission peak intensities of the ZnO nanoparticles synthesized at different conditions were monitored during wet-chemical reactions. It was shown that the three stages of the reaction; nucleation, growth, and reaching the average size, can be followed by means of the fluorescence intensities corresponding to both bandedge (similar to 375 nm, similar to 445 nm, and similar to 485 nm) and deep-trap (similar to 520 nm and similar to 545 nm) transitions. With both higher stirring velocity and temperature the particle formation is faster. Although the nucleation time is not affected by stirring velocity, higher temperature causes faster reaction rate in all stages including nucleation. This method can be used for controlling the size of the nanoparticles. (C) 2013 Elsevier B.V. All rights reserved.