The force needed to remove spherical toner particles having a number average radius of 7.1 μm from an organic photoconductor was determined by ultracentrifugation. It was found that only a small fraction of the toner particles could be removed from the photoconductor, even at the highest centrifugal accelerations (354,000g) from the bare photoconductor. However, when the photoconductor was coated with a thin layer of zinc stearate, toner removal was readily achieved. It was found that the release force from the zinc stearate-coated photoconductor varied with the square of the toner charge-to-mass ratio. These results suggest that, while both van der Waals and electrostatic forces contribute to the adhesive interaction between toner particle and photoconductors, the van der Waals forces dominate for this size particle in the absence of release agents. Conversely, in the presence of good release agents, van der Waals forces can be reduced to a level where they are comparable or smaller than electrostatic interactions.