Systems, methods, and interfaces are described herein for identification of effective electrodes to be used in sensing and/or therapy. Two or more portions of a signal monitored using an electrode may be compared to determine whether the electrode is effective. The two or more portions may correspond to the same portion or window of a cardiac cycle. Further, signals from a first electrode and from a second electrode located proximate the first electrode may be compared to determine whether one or both of the electrodes are effective.