Resynchronization of the failing ventricle is currently achieved by pacing the left and right ventricles simultaneously with specialized electrodes and a cardiac stimulator. However, controversy persists concerning the optimal configuration for cardiac pacing in these patients. Right ventricular pacing alone has been shown to be deleterious in some patient populations. The benefits of biventricular pacing in heart failure patients may be due primarily to left ventricular stimulation and may, in some patients, be decreased by the presence of simultaneous RV stimulation. Preliminary data from our own animal work suggest that in the majority of cases, LV stimulation alone is better than RV stimulation, and that BiV stimulation represents an intermediary situation between LV and RV stimulation.