Along with angiogenesis and gene therapy, cell transplantation is one of the newest treatment modalities proposed to improve the outcome of patients with cardiac failure. Both experimental and clinical data have now established that implantation of contractile cells into fibrous postinfarction scars can allow them to regain some functionality. Primarily for practical reasons, autologous skeletal myoblasts have been the first to be tested in a clinical trial, but other cell types can be considered among which bone marrow stromal and hematopoietic stem cells are of particular interest because of their presumed pluripotentiality and the possibility to use them as autografts. However, several key issues still need to be addressed including: (1) the advantages and disadvantages of these different donor cells; (2) the extent to which cell engraftment affects cardiac function actively (ie, by increasing contractility) or passively (ie, by limiting infarct expansion and remodeling); (3) the development of strategies targeted at enhancing cell survival; and (4) the identification of cardiac diseases for which cell engraftment may be most beneficial. In parallel to the numerous experimental studies designed to address these issues, initial clinical trials are underway or in preparation and it is mandatory to design and conduct them in a careful manner so as to ultimately know whether cellular transplantation holds its promise as a means of improving the outcomes of patients with heart failure. Copyright 2002, Elsevier Science (USA). All rights reserved.