Improvement in the methodological approach to the analysis of the myocardium has provided clear evidence of cardiac myocyte proliferation, questioning the general belief that the growth of the adult heart under physiological and pathological conditions can occur only by cellular hypertrophy. Myocyte regeneration contributes via myocyte death to the physiological turnover of myocytes and via myocyte hypertrophy to cardiac remodeling. Several questions, however, remain to be answered. Among them, it is still unknown whether myocyte multiplication exerts a positive and/or negative effect on ventricular anatomy and cardiac function. The addition of newly generated myocytes leads to cavitary dilation with relative thinning of the wall. Conversely, myocyte proliferation, characterized by the parallel addition of cells, can be expected to increase wall thickness, decrease chamber size, and ameliorate cardiac performance.