Toner is charged and transferred to the developing area in the development cartridge of a laser beam printer on a development roller. Optimum toner charging and mass transfer are important factors to produce fine images with high quality. The charging mechanism of toners in the electrophotogaphic mono-component developing system was studied in this work. Two different kinds of mono-component nonmagnetic toners were used. One was a polymerized toner (spherical), and the other was a pulverized toner (irregular). The dynamics of toner charging were investigated by using a microscopic current measurement technique. A current was observed to flow through each system part (i.e. development roller, blade and supply roller) during the roller rotation with toner attached on its surface. Development rollers with various surface properties were prepared for this study. Currents and toner charge to mass values were measured for each roller for the two different toners. It was found that the current had a strong relationship to the toner charge and mass. It was also conjectured that the current and toner charge are related to the movement of toner at the blade. (C) 2003 Elsevier B.V All rights reserved.