Objective To investigate the efficacy of autologous bone marrow mononuclear cells transplantation in treating lower l imb thromboangiitis obl iterans (TAO). Methods From January 2005 to November 2008, 25 patients (27 l imbs) with lower l imb TAO were treated. There were 24 males (26 l imbs) and 1 female (1 l imb), aging 16-44 years (33 years on average). Fifteen left l imbs and 12 right l imbs were involved. The median duration of disease was 2 years (from 3 months to9 years). Intermittent claudication was observed in 5 cases (5 l imbs), 16 patients (17 l imbs) had symptom of rest pain, 4 patients (5 l imbs) suffered ulcer on the distal l imbs. The results of visual analogue scale (VAS), maximum walking distance (MWD), ankle/brachial index (ABI), and transcutaneous oxygen pressure (TcPO2) before operation were (7.16 ± 1.12) points, (0.098 ± 0.043) km, 0.20 ± 0.09, and (11.78 ± 3.46) mm Hg (1 mm Hg=0.133 kPa), respectively. A total of 300 mL bone-marrow blood was extracted from the il iac bone. And then the mononuclear cells were isolated from the bone-marrow blood. All patients received cell transplantation only one time. The amount of transplantation bone marrow mononuclear cells was (1.82-29.46) × 109 (mean 13.33 × 109). Results All patients were followed up for 1 years. After 4 weeks of implantation, the results of VAS, MWD, ABI, and TcPO2 were (2.39 ± 0.51) points, (0.783 ± 0.176) km, 0.28 ± 0.16, (21.33 ± 6.57) mm Hg, respectively, showing significant difference compared with preoperative results (P lt; 0.05). The VAS, MWD, ABI, and TcPO2 increased to (2.44 ± 0.67) points, (1.199 ± 0.304) km, 0.37 ± 0.09, (27.90 ± 5.23) mm Hg after 1 year of implantation, showing significant differences compared with preoperative results (P lt; 0.05). One ulcer healed well and the improvement was obtained in other 3 cases after 4 weeks of implantation (80%). Four ulcers healed well after 1 year of implantation (80%). After 1 year of implantation, angiography revealed 37.04% affected limbs had a satisfactory neovascularization. The angiographic levels were grade 0 in 5 cases, grade 1 in 12 cases, grade 2 in 4 cases, and grade 3 in 6 cases. Conclusion Autologous bone marrow mononuclear cells transplantation could be a simple, safe, effective method to treat TAO.