Background Transient ischemic attacks are common. Approximately 15% of stroke victims report prior TIAs, and 300 000 TIAs are reported annually in the US. TIAs are usually brief, and most patients have returned to baseline by the time of their ED evaluation. While antiplatelet agents and anticoagulants for atrial fibrillation are known to decrease stroke risk, the need for urgent intervention is not clear. A paucity of studies describing the natural history of TIA has led to marked practice variation.