To control and understand the influence of different process parameters on the formation of nanoparticles, it is necessary to determine the primary particle size which is beside others one of the most crucial parameters for particle quality. An appropriate fast and nonintrusive measurement technique for online and in situ determination is time-resolved laser-induced incandescence (TIRE-LII). Investigations in different reactors have been carried out to characterize different kinds of nanoparticles. Beside the process control of carbon blacks, also the capability of this measurement technique to determine other nanoscaled particles are shown and discussed. Therefore, investigations in a low pressure vaporization and a CO2-laser vaporization reactor various metals and metal oxides are accomplished.