The dynamics of toner and carrier particles in a two-component development system used in electrophotography were studied to clarify the development characteristics and to reduce the image defects due to the bead-carry-out (BCO) phenomenon. The height of the developed toner line image and the density of carrier particles adhered to the photoreceptor surface after development were measured and the behavior of the toner and carrier particles was observed using a high-speed microscope camera. This study clarifies that development occurs not only in the contact area between the carrier brush and the photoreceptor but also in the pre- and postnip regions where the brush does not make contact with the photoreceptor and that the occurrence of BCO is reduced in the image area rather than in the nonimage area at a low dc development voltage at a high toner concentration and with the development sleeve at a high-speed ratio. The mechanisms of these phenomena are investigated using independent experimental and numerical analysis.