The deposition of toner on a latent electrostatic image is a function of the toner flow rate in the development region of a dual-component magnetic brush development system. Some models have been previously proposed to describe the dependence of development on the speed ratio between the magnetic brush and the recording medium. We propose an improved toner flow model that considers the speed difference between the developer brush and the electrostatic image. This model presents the toner flow mass as a function of the product of the brush speed ratio and a saturation function of the brush speed difference. The model is useful for predicting the deposited toner mass and optical image density when the development conditions are changed. Analytical and experimental studies are described. The experimental results correspond well with the calculated results.