The purpose of this article is to review the use of Doppler echocardiography for assessing responses during cardiac pacing. Doppler techniques allow the physician to select the optimal mode pacemaker and pacemaker settings with regard to heart rate and atrioventricular delay, at rest and during exercise. Doppler parameters can be used to predict the relative hemodynamic advantage of dual chamber or rate adaptive pacing over fixed rate pacing. This valuable noninvasive modality may enhance the benefit of pacemaker therapy.