Critical limb ischemia (CLI) continues to be an important cause of atherosclerotic morbidity and mortality despite conventional therapies. Modulation of angiogenesis is a promising alternative to surgical revascularization. Trials of isolated angiogenic growth factor therapies using recombinant proteins or gene transfer have been conducted, but with disappointing results because it is unlikely that a single angiogenic factor is solely or even primarily responsible for angiogenesis. Emerging stem cell therapies represent a new approach to the modulation of angiogenesis. Pluripotent hematopoietic stem cells (HSC) hold promise because they can reproduce a pro-angiogenic milieu in the ischemic limb rather than upregulate a single angiogenic factor.