Bone marrow is a reservoir for hematopoietic stem cells, endothelial precursor cells, and bone marrow stromal cells (also generally called mesenchymal stem cells), whose positive role in tissue repair is highly anticipated. In this report, we introduce a novel function of substance-P (SP), an 11-amino-acid peptide, as an injury-inducible messenger to mobilize bone marrow stem cells to the blood and finally to engage in tissue repair. This new drug may substitute for ex vivo cell culture of therapeutic cells by stimulating cell proliferation in the bone marrow in vivo and mobilizing those therapeutic cells to the patient's own blood stream. Again, the additional role of SP in mitigating inflammation-mediated tissue damage can further rationalize the clinical development of SP-peptide as a stem cell stimulant.