Magnetic resonance imaging of the optic nerve and spinal cord in multiple sclerosis has advanced considerably in the past decade. It is possible to reliably detect intrinsic optic nerve and spinal cord lesions due to demyelinating disease. Detection of these can assist diagnosis, especially in the spinal cord. As demyelinating lesions in these structures are often symptomatic, MR imaging in these regions also provides a special opportunity to obtain insights into pathophysiological and pathogenetic mechanisms.