A wide variety of surface modified fumed metallic oxides has been proposed and successfully applied as toner additives for improvement of such characteristics as free-flow properties, tribo-electrostatic charge (ESC) level, and charge stability at the activation time and ambient variations. When the Selenium (Se) was mainly used as image drum component, dimethylsilyl treated fumed silica with negative charge was an effective additive. According to the introduction of the new technologies, such as Organic Photo Conductor (OPC) or amorphous silicon (a-Si) drum, the requirements for the toner, and hence for the toner additives have diversified extensively. The type of polymer for toner, e.g. polystyrene-acrylic type or polyester type, and the type of the machine, e.g. monochrome, color or multifunctional unit, also helped diversification of such requirements. To meet with the specific requirement in the respective system, the various surface modified fumed oxides, ranging from positive charged to negative charged, from high BET surface fine particles to low BET coarse particles, for example, have been developed. This paper describes the typical proposed material designed to suit for the respective system, with the physicochemical data, and then discusses the effect of the types of surface treatment reagents on the performance of the toner.