Cell transplantation is currently gaining a growing interest as a potential new means of improving the prognosis of patients with cardiac failure. The basic assumption is that left ventricular dysfunction is primarily caused by the loss of a critical number of cardiomyocytes and that their replacement by new contractile cells could functionally 'regenerate' postinfarction scars in which these cells are implanted. Primarily for practical reasons, autologous skeletal myoblasts have been the first to undergo clinical trials but other cell types are also considered, particularly bone marrow stem cells which are attractive because of their autologous origin and their purported cardiomyocyte/endothelial transdifferentiation potential in response to cues present in the target organ. However, several key issues still need to be addressed including (1) the optimal type of donor cells, (2) the mechanism by which cell engraftment improves cardiac function, (3) the optimization of cell survival, and (4) the potential benefits of cell transplantation in nonischemic dilated cardiomyopathies. In parallel to the experimental studies designed to address these issues, clinical trials are underway and their results should hopefully allow the assessment of to what extent cellular therapy may improve the outcome of patients with heart failure. © 2003 European Society of Cardiology. Published by Elsevier Science B.V. All rights reserved.