Abstract: A multi-lead ECG monitor which determines whether the reference electrode has been disconnected and, if so, switches to another reference electrode to continue ECG monitoring. Disconnection of the reference electrode can be determined by observing that no ECG signal is being received from any of the electrodes. When this is detected, the reference electrode is switched to another electrode which is selected in accordance with a predetermined priority scheme. After a stabilization period, the system then determines if any electrodes are still connected. If not, then, as before, it is determined that the new reference electrode is not connected and that a new reference electrode needs to be selected. The switching of the reference electrode continues in this manner until it is determined that electrodes are connected.