This chapter reviews the evidence that blood is readily identifiable on magnetic resonance imaging (MRI). It describes how the use of multiple sequences provides additional information regarding the age of blood products. MRI signal changes on gradient recalled echo (GRE), T1- and T2-weighted images can be used to estimate the age of intracranial blood. MRI is the initial diagnostic procedure of choice for investigation of underlying structural causes of secondary intracerebral hemorrhage (ICH), including vascular malformations and neoplasms. It is generally recognized that MRI is superior to computed tomography (CT) in the evaluation of subarachnoid space diseases of an inflammatory or neoplastic origin. The existence and nature of the penumbra in ICH is arguably the most pressing outstanding information required by clinicians to make rational management decisions in ICH patients. MRI is a valuable tool for investigating the pathophysiology of acute and chronic ICH.