Candidate cells for the repair of the myocardium include mature cardiomyocytes and stem/progenitor cells. The former have been shown to be involved in regeneration of zebrafish and neonatal mouse hearts after damage or loss, but in neither case can a role for stem/progenitor cells be excluded. Furthermore, the ability of cardiomyocytes to re-enter the cell cycle, a necessary prerequisite for their involvement in regeneration, appears to be substantially diminished in the adult mammalian heart. A range of markers and methods have been used to identify stem/progenitor cells in the adult heart and some of these have been linked to cells seen during embryonic development. An attractive property of such cells would be multi-potentiality such that the endothelial and smooth muscle cells of the heart could be repaired or replaced at the same time as the myocardium. This property has been attributed to a subset of the candidate stem/progenitor cells reported to date. We have been studying the development of the heart using zebrafish and the amphibian, Xenopus, as models, and have discovered that the cardiac programme is closely related to the blood and endothelial programmes early in development. Indeed we have shown that they share master regulators but then that they become differentiated by virtue of FGF signalling which sets up cross-antagonistic interactions between transcriptional regulators specific to one or other tissue. We have proposed that, by extending the domain of influence of FGF signalling during evolution, the population of blood and endothelial precursors found adjacent to the heart in zebrafish and Xenopus have been recruited into the heart field to generate the bigger multi-chambered heart found in amniotes including mammals. The significance of this model for stem/progenitor cells in the adult heart may lie in the evolutionary memory, of the endothelial programme for example, retained in these more recently recruited cells. An example is the cell population expressing the transcription factor, Islet1, observed in the neonatal heart. In the embryo Islet1 marks the precursors of the second heart field which may represent this more recently recruited population. We have obtained data showing that Islet1 does indeed control the blood and endothelial programmes as well as the myocardial programme in Xenopus embryos. This role for Islet1 is downstream of Wnt and BMP signalling. A better understanding of the origins of candidate stem/progenitor cells and their programming may allow their manipulation for cardiac repair in the future.