Transient global amnesia represents an episode of acute onset of transient global anterograde amnesia, with a variable degree of impairment of retrograde memory, which is not associated with any other major neurologic signs or symptoms. Resolution is gradual, with subjective recovery occurring in two thirds of patients within 2 to 12 hours and, in almost all, within 24 hours. In this clinical article, Dr. Alfredo Ardila explains that the etiology is still controversial and could be explained by an ischemic event due to arterial thromboembolic ischemia in a subgroup of patients with increased vascular risk factors. PET studies usually show hypometabolism in the hippocampi and mesial temporal lobes. An acute effect on hippocampal cornu ammonis neurons has been proposed as the functional correlate of amnesia, reflecting a transient disruption in the hippocampus memory circuits. Recently, it has been suggested that not only memory is affected, but also executive functions are diminished.