Bone marrow implantation (BMI) has been utilized for the treatment of limb ischemia, however, serum markers have not yet been reported to express the degree of limb ischemia. We analyzed the serum levels of several cytokines including erythropoietin (EPO) in the treated legs and the contralateral ones in 11 patients with limb ischemia treated with BMI. The EPO level in the pre-treated legs in the 5 patients with arteriosclerosis obliterans revealed a good correlation with ankle-brachial pressure index. The EPO level, but not the levels of TNF-alpha, VEGF, and bFGF in the pre-treated legs was significantly higher than that in the contralateral legs in the 11 patients, and the EPO level decreased in 4 weeks after BMI. The serum EPO level may express the degree of limb ischemia presumably through the reactive production of EPO in ischemic tissue.