Cell transplantation is emerging as a new treatment designed tot improve the poor outcome of patients with cardiac failure. Its rationale is that implantation of contractile cells into postinfarction scars can functionally rejuvenate these areas. Primarily for practical reasons, autologous skeletal myoblasts have been the first to be tested clinically but bone marrow stromal and hematopoietic stem cells may represent an interesting alternative in select situations because of their autologous origin and their purported plasticity. However, several key issues still need to be addressed including (1) the optimal type of cells, (2) the mechanism by which cell engraftment improves cardiac function, i.e., increased contractility or limitation of remodeling, (3) the most effective strategies for optimizing cell survival, and (4) the potential benefits of cell transplantation in nonischemic heart failure. In parallel to the experimental studies designed to address these issues, initial clinical trials are underway and should hopefully allow to know whether the hopes raised by cellular therapy are met by clinically meaningful improvements in function and outcome in patients with severe left ventricular ischemic dysfunction.