Transient global amnesia is a momentary neurological accident frequently encountered in subjects over 50 years of age. Its diagnosis is purely clinical and rests on the sudden occurrence of retention amnesia associated with retrograde amnesia without disturbances in speech or other neurological deficits. The amnesia totally regresses within less than 24 hours. Paraclinical examinations add nothing to the diagnosis. The cause of transient global amnesia is unknown, and the various hypotheses that have been put forward (e.g. epilepsy, transient ischaemia or migraine) have not been confirmed by clinical and epidemiological studies. Despite a low, but real risk of recurrence, the prognosis is perfectly benign, and there is no need for curative or preventive treatment.