Clinicians should take a mechanistic approach to transient ischemic attack and stroke. Distinguishing between hemorrhagic and ischemic stroke is important and is most readily accomplished with a computed tomographic brain scan. Newer diagnostic studies are now available to help evaluate patients for a cardiogenic source of embolism. Detection of a cardiogenic source of embolism or high-grade carotid stenosis identifies stroke-prone persons in whom interventional therapy is beneficial.