Alarms in ambulatory monitoring of electrocardiography (ECG) sound in our cardiology ward too frequently. To investigate the incidence and causes of inadequate alarms, we examined 3,699 alarms in a total of 100 inpatients during a period of 7 days retrospectively. Of the alarms, 49% was related to extreme bradycardia, 31% to extreme tachycardia and 10% to trained ventricular premature beats. Alarms were set off because of correct detection of cardiac abnormalities (50%), poor electrode-to- patient contact (17%) and wrong diagnosis (12%), and body movement of patients (11%). To reduce false alarms in ambulatory ECG monitoring, we though it would be necessary to (1) change electrodes once a day, (2) wipe the sweat from the patient’s chest surface, (3) stick electrodes away from movement sites, (4) tape down lead wires to prevent them from pulling on the electrodes, (5) select sticking sites to get enough QRS voltage (›1mV), and (6) set adequate threshold of heart rate to make alarms.