Although the symptom of headache is a frequent cause of Emergency Department examinations, it is often considered to be of little clinical relevance in comparison with other emergencies and is usually treated only symptomatically. But how frequently does a simple headache mask a severe cerebral pathology? To answer this question, we studied a consecutive series of patients examined at the Neurology Emergency Department of Turin's Ospedale Molinette over a period of three months; the patients were then followed-up for more than two years in order to confirm the diagnoses. Of 215 cases of "acute" headache, 121 (56%) were essential and 94 (44%) symptomatic; of the latter, 18 (8.3%) were the only clinical manifestation of a severe cerebral pathology (10 hemorrhages, 2 ischemias, 6 tumours). In diagnosing these 18 cases, 72 EEG, 57 CT and 4 rachicentesis examinations were carried out and their diagnostic efficacy is here analysed. Our data show the importance of a careful evaluation of the symptom of headache in Emergency Departments and the need to send any doubtful cases to a facility specialised in coping with such emergencies.