Susceptibility-weighted imaging (SWI) has proven to be a very sensitive technique for the identification of cerebral microbleeds (CMBs). Increased sensitivity to CMBs may allow assessment of the rate of microhemorrhage development or regression, allowing more precise analysis of the natural history of disease, or better assessment of response to therapy. Early recognition may be advantageous to patients treated with anticoagulant or aspirin therapy in that they are at increased risk for subsequent and possibly fatal hemorrhage. There are in the order of 1.4 million people a year affected by traumatic brain injury (TBI). For these patients, computed tomography (CT) is the mainstay of imaging in the emergency setting and does a good job detecting major bleeds. Radiation damage to blood vessels and radiation necrosis can result from treating tumors and disease with potentially damaging doses of radiation. Future semiautomated methods hold promise for evaluating large numbers of patients using SWI.