Electrocardiographic abnormalities associated with intracranial diseases, especially subarachnoid hemorrhage, are well known, while there is hardly mention of cardiac arrhythmias in the neurological and cardiological literature. In order to assess the incidence of arrhythmias 52 consecutive patients with subarachnoid hemorrhage secondary to ruptured aneurysm were investigated with 24-hour Holter recordings. Bradyarrhythmias and tachyarrhythmias were found in 46 patients (88%); premature ventricular beats in 25 pts (12 of these in 3rd-5th Lown classes), ventricular tachycardia in 2, premature supraventricular beats in 14, paroxysmal atrial fibrillation in 1, sinoatrial blocks and arrests in 18, atrioventricular dissociation in 2 and idioventricular rythm in 2. Moreover in 5 pts ST segment changes were found, suggestive of transitory acute myocardial ischemia. The presence and severity of arrhythmias were correlated with the time elapsed from the episode of bleeding, with the QT interval, and with the hemorrhage extent. Our results indicate an high incidence of arrhythmias in subarachnoid hemorrhage, sometimes serious mainly in early stage. Continuous electrocardiographic monitoring is therefore extremely useful and provides data for therapeutic consideration.