Susceptibility-weighted imaging (SWI) is a recently developed magnetic resonance imaging (MRI) technique where image contrast represents ‘magnetic susceptibility effects’—a natural property of tissues. The applications of SWI are rapidly increasing, with much work being carried out to determine the usefulness of the technique in multiple disease states. Current clinical applications of the technique include detection of microbleeds, subarachnoid hemorrhage (SAH), ferromagnetic deposition in neurodegenerative disease, and characterization of cerebral tumors.