Thirty two patient with a history of brief unconsciousness underwent a constant ECG monitoring with Holter's technique for 24-72 hours. Syncope was noted in 16 patients. Cardiac arrhythmia was a cause of unconsciousness in 14 patients whereas no such a pathology was seen in the remaining two patients. No syncope was seen during ECG monitoring in 16 patients. Loss of consciousness was found in the majority of patients monitored for 72 hours. This technique may be valuable in the diagnosis of syncope, especially when it appears during ECG monitoring.