pX×üúd@Éaeé SnO 2 im±q̱aªz nÚ`¾E²¡ö×EnLiE3 éÞ Eºä[êÞ E¼vKÞ E] ÌØÞ Eªä òÞThe variation in particle size distribution of SnO 2 nanoparticles by the pulsed wire discharge (PWD) process has been clarified. Special attention has been paid for the influence of both synthesis conditions of ambient pressure and charging voltage on the distribution. The geometric standard deviation (s g ) and the count mean diameter (d ) were clearly influenced by these conditions. This can be summarized by means of a parameter being propor tional to the plasma expansion volume. It was found that s g and d monotonically decreased with increasing this parameter. This tendency can be explained by the reported results of numerical simulations in which both coagu lation and chemical reaction in the free molecule regime are taken into account, indicating that a relatively slow reaction rate compared to the coagulation rate broadens the particle size distribution during PWD process.