Adult human bone marrow and peripheral blood contain diverse stem and progenitor cells with some properties resembling those of embryonic stem cells, as this has been revealed by an increasing body of evidence within the near past. Numerous in vitro experiments and subsequent animal studies have already demonstrated that these adult progenitor cells considerably contribute to the regeneration of ischemic or injured tissue. Over the last 4 years, several clinical studies employing such a hypothesis in the context of myocardial repair after acute infarction or during chronic ischemic heart disease have been published. These studies have used autologous bone marrow- as well as peripheral blood-derived progenitor cells, which were delivered via intracoronary or intramyocardial routes near the ischemic area. The initial results demonstrated the safety and possible benefit of this strategy, which appears to be relatively inexpensive and free of side effects. However, the present clinical studies were small in size so that the overall therapeutic efficacy remains open to debate and evaluation. Furthermore, a major part of the underlying repair mechanisms has been proposed but not yet elaborated. Hence, larger case-controlled, randomized and double-blinded trials in addition to experimental investigations on the primary molecular mechanisms of myocardial repair are crucial for the future.