 There is evidence in animal and clinical studies that adult stem cells in the bone marrow, called endothelial progenitor cells, participate in the development of new blood vessels, a process called angiogenesis. In this investigation, patients with limb threatening ischemia will have their bone marrow harvested and the stem cells will then be removed and injected directly into the muscle of the diseased leg. The procedure will require about 4 hours and the subjects will be admitted to the Indiana University Medical Center overnight. The follow-up period is 12 weeks and the analysis will consist of examinations at 1, 2, 4, 6, 8, and 12 weeks. Adverse and serious adverse events will be recorded during this time period. Diagnostic studies will be obtained to measure blood flow in the treated leg during the follow up period and include transcutaneous skin oxygen measurements, pressure recordings in the leg, arteriography, magnetic resonance imaging, and wound healing. 