In a case of repeated syncope of abrupt onset and questionable origin, we utilized the continuous ambulatory cassette recorder to document simultaneous electroencephalography/electrocardiography (EEG/ECG) changes. Recording during a spontaneous episode established the cardiogenic origin. Problems in differential diagnosis of syncope and seizure are discussed. With this new instrument, if the initial event in ECG abnormality (as in the present case), further cardiologic study is indicated. If epileptiform EEG activity is primary, neurologic investigation is the direction to pursue; if there is nonepileptiform EEG slowing without ECG abnormality, diagnosis of syncope of noncardiac origin (e.g., hypotension, hypoglycemia) should be considered.