Umbilical cord blood (UCB) represents a readily available source of hematopoietic and endothelial precursors at early ontogeny. Understanding the proangiogenic functions of these somatic progenitor subtypes after transplantation is integral to the development of improved cell-based therapies to treat ischemic diseases. We used fluorescence-activated cell sorting to purify a rare (<0.5%) population of UCB cells with high aldehyde dehydrogenase (ALDH hi ) activity, a conserved stem/progenitor cell function. ALDH hi cells were depleted of mature monocytes and T-and B-lymphocytes and were enriched for early myeloid (CD33) and stem cell-associated (CD34, CD133, and CD117) phenotypes.