Background and Objectives: We designed this study to determine the therapeutic potentials of umbilical cord blood (UCB)-mesenchymal stem cells (MSCs), as compared with bone marrow (BM)-MSCs. Materials and Methods: MSCs were isolated from UCB and BM. For the in vivo study, myocardial infarction was induced by ligation of the left anterior descending coronary artery (LAD) in rats for 30 min, and this was followed by release; the MSCs were then injected into a designated point around the infarcted area. Echocardiographs were performed two weeks after surgery. For the in vitro study, a cDNA microarray and cytokine array were performed to compare the MSCs from UCB and from BM. Cell migration was assessed by a wound scratch assay, and the level of cardiac ankyrin repeat protein (CARP) was determined by reverse transcriptase-polymer chain reaction (RT-PCR) or Western blot analysis. Results: For the echocardiograph findings, the fractional shortening (FS) was 43.9% in the UCB-MSCs gro