A study was conducted to better understand the toner charging process under dynamic conditions. A second study was conducted to better understand how toner chargeability is affected by the aging of the components in the printer cartridge of single component electrophotography-based toner printing systems. In this article the authors report on both of these studies. In these systems, toner is tribocharged, i.e., charged by friction by contact with the component surfaces in the printer cartridge. Through a series of experiments it was observed that the nip between the developer and the supply roller is the primary charging region, which was further augmented by the metering blade. In the second study a significant reduction in the charging ability of the toner was observed as the printing cartridge aged due to wear of the toner and the charge contributing components in the cartridge. As efforts continue to be made to place single component toner development technology at the forefront of affordable, reliable, and high quality printing, it has become very important to better understand these issues.