Blood-derived circulatory angiogenic cells (CACs) and resident cardiac stem cells (CSCs) have both been shown to improve cardiac function after myocardial infarction. The superiority of either cell type has long been an area of speculation with no definitive head-to-head trial. In this study, we compared the effect of human CACs and CSCs, alone or in combination, on myocardial function in an immunodeficient mouse model of myocardial infarction.