The purpose of this study is to learn more about stroke and obtain information that may serve as the basis for future investigations. It will 1) establish a registry of patients with cerebrovascular disease (stroke); 2) characterize the natural history of acute stroke and transient ischemic attacks (TIA)-an interruption of blood flow to the brain that causes stroke symptoms for a short period of time); and 3) evaluate the data to generate ideas for future studies. Patients 18 years of age or older with suspected acute stroke or TIA may be eligible for this study. Subjects will be recruited from patients who present with stroke at the emergency department of Suburban Hospital in Bethesda, Maryland. The study will gather data collected from diagnostic and laboratory tests the patient undergoes as part of standard medical care, including findings of medical and neurological examinations and other tests. In addition, studies will be done for research purposes only to gather data about stroke and TIA. These may include the following: * Blood and urine tests not more than 2 tablespoons of blood will be drawn for various tests. * Electrocardiogram (EKG) (heart tracing)-electrodes placed on the chest wall detect the heartbeat and heart rhythm. * Computed tomography (CT) scan of the head-specialized X-rays are used to obtain images of the brain. * Magnetic resonance imaging (MRI) of the brain-a strong magnetic field and radio waves are used to produce images that provide information about the brain tissue and blood vessels. * Transcranial Doppler (TCD)-sound waves are used to image the arteries of the brain and neck. * Echocardiogram-sound waves are used to image the heart and evaluate heart function. Patients may be asked to return to Suburban Hospital for follow-up testing in 1, 3, and/or 12 months, when some of these tests may be repeated to assess changes over time ...