Biventricular pacing has been consistently shown to improve symptoms and exercise capacity in patients with advanced heart failure and wide QRS complexes. Recent data have shown that biventricular pacing has the propensity to reduce left ventricular volume, a condition referred to as reverse remodeling. Since the authors initial description of successful left ventricular reverse remodeling after biventricular pacing therapy, data from multicenter trials have grown and consistently support the observation. In addition to the volumetric change, there was also progressive improvement of left ventricular systolic function and clinical status. The authors subsequent data also illustrated that the benefits on reverse remodeling and left ventricular systolic function were pacing dependent and disappeared gradually when pacing was withdrawn. With the use of tissue Doppler imaging, a substantial proportion of patients were found who had mechanical delay in the free wall. During biventricular pacing, all the segments were homogenously delayed resulting in a late, albeit synchronous, systolic contraction.