Abstract: Ultrasmall superparamagnetic iron oxide (USPIO) are dextran-coated iron oxide nanoparticles that are internalized into a variety of cells, among which are mainly cells of the mononuclear phagocytic system. Owing to the presence of iron, they produce a susceptibility effect that is observable on T2- and T2^*-weighted MR images as low signal intensity, Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system. Experimental autoimmune encephalomyelitis (EAE) is a commonly used animal model. T cells and macrophages play an important role in disease initiation and progression in MS and EAE. They are involved in different phases of disease, MRI with USPIO can monitor inflammation in MS and EAE in vivo. This MRI technique has great importance in monitoring 6isease relapse, development, and therapeutic effect.