Routine electroencephalography (EEG) suffers from the same problem as a standard 12 lead electrocardiogram (ECG): it is limited in time. A standard ECG captures 10 seconds of the heart’s electrical activity while a standard EEG captures perhaps 10 to 20 minutes of the brain’s electrical activity. While these studies have their respective places in diagnostic medicine, they are limited in their ability to detect sporadic events such as paroxysmal atrial fibrillation in the former case, or a seizure event in the latter. Just as cardiologists have adopted Holter monitoring into clinical practice, so too have neurologists turned to ambulatory EEG for certain diagnostic purposes. We discuss the clinical indications for ambulatory EEG.