Acute global amnesia may be due to several causes, such as transient global amnesia (TGA), acute drug-related confusional state, toxic substances, metabolic abnormalities, infective diseases, cerebral tumours, cerebrovascular accidents, subarachnoid haemorrhage and epilepsy. In particular both TGA and subarachnoid haemorrhage may be precipitated by sexual activity; by contrast the two diseases are quite different in prognosis and treatment. Ten subjects were admitted in the period 1997-99 to our emergency department for acute global amnesia related to sexual activity. They represented 18% of total acute global amnesias observed in the same period. All patients were males, aged between 41 and 64 years. TGA was found in nine cases, while one patient had subarachnoid haemorrhage, due to rupture of an aneurysm of the right middle cerebral artery. The patient with subarachnoid haemorrhage showed neurologic defects (second-degree nystagmus and retropulsion), while no major neurologic abnormalities were found in TGA. Likewise computerized tomography (CT) scan was positive only in the case of subarachnoid haemorrhage. Patients and relatives in most cases left out sexual activity as a trigger factor. This experience indicates that acute global amnesia related to sexual activity is mostly due to TGA. Major neurologic signs are suggestive of subarachnoid haemorrhage and an immediate CT scan is recommended. Targeted questions are needed to identify the cause of the event.