Pigment nanoparticles with a size range of 10~100 nm were produced from large agglomerates via a stirred media mill operating in the wet-batch mode and using polymeric media. The effects of several operating variables such as the surfactant concentration, polystyrene media loading, and media size on the pigment size distribution of the product were studied. The process dynamics was also investigated. Dynamic light scattering and electron microscopy were used as the characterization techniques. The polymeric grinding media are found to be effective for the production of pigment nanoparticles. The experimental results suggest the existence of an optimum media size and surfactant concentration. A population balance model of the process reveals a transition from first-order breakage kinetics for rela-tively coarse particles to non-first-order kinetics, with a delay period, for the smaller particles. The model implies that large agglomerates split in a first-order fashion whereas the breakage of individual nanoparticles may depend on induced fatigue of the particles. Pigment nanoparticles with a size range of 10 ~ 100 nm were produced from large agglomerates via a stirred media mill operating in the wet-batch mode and using polymeric media. The effects of several operating variables such as the surfactant concentration, media size on the pigment size distribution of the product were studied. The process dynamics was also investigated. Dynamic light scattering and electron microscopy were used as the characterization techniques. The polymeric grinding media are found to be effective for the production of pigment nanoparticles. experimental results suggest the existence of an optimum media size and surfactant concentration. A population balance model of the process reveals a transition from first-order breakage kinetics for rela-tively coarse particles to non-first-order kinetics, with a delay period, for the smaller particles. The model implies that large agglomerates split in a first-order fashion while the breaka ge of individual nanoparticles may depend on induced fatigue of the particles.