Transient global amnesia (TGA) has been defined as the presence of an impairment of short-term memory, retrograde amnesia and repetitive queries, without any other neurological signs or symptoms. The precise pathophysiology of TGA is unclear, although thromboembolic, epileptic, migrainous and metabolic mechanisms have been suggested. We have studied the clinical, biohumoral, electroencephalographic and neuro-imaging data relating to 25 patients with TGA, and found a prevalence of hypertension and hypercholesterolemia. We also found a higher incidence of electrical changes in the patients whose TGA was of shorter duration, whereas brain CT scans revealed ischemic lesions more frequently in the patients with TGA of longer duration. Our findings seem to confirm the hypothesis that TGA is a heterogeneous clinical syndrome consisting of pure and ischemic forms.