4,4'-bis(1'-Azo-2'-hydroxy-3'-naphthoyl-o-chloroanide) oxazole (AZO) nanoparticles in size of 40-60 nm were prepared by the method of liquid phase surfactant-assisted reprecipitation. The AZO nanoparticles were characterized by UV/VIS absorption, X-ray diffraction pattern, and TEM measurements. It revealed that AZO nanoparticles were near spherical in shape and were in amorphous state. The photoconductivity of AZO nanoparticles in single-layered photoreceptors was studied as well. The results showed that the photoconductivity of AZO nanoparticles was improved greatly compared to that of bulk AZO due to nanometer size effect. (C) 2004 Kluwer Academic Publishers.