Objective:We investigated the effect of immersion of feet in CO 2 -enriched water for preventing expansion and formation of ischemic ulcer in critical limb ischemia of diabetic patients after surgical revascularization. Materials and methods: Eligible patients were allocated CO 2 group (CO 2 immersion plus standard care) or control group (standard care alone) and were followed up for 3 months after surgical revascularization. The end point is defined as an expansion of a target ulcer (more than 101% of original size) or the formation of new ulcers during the follow-up period. Results: Fifty-nine patients out of originally enrolled 66 patients with type II diabetes were included in intention-to-treat population. The cumulative prevention rate for ischemic ulcer after 3 months was 97.1% in the CO 2 group, while, in the control group, it was 77.8%, i.e., significantly lower than the CO 2 group ( P = 0.012, log-rank test). The transcutaneous oxygen pressure increased significantly only in the CO 2 group, from 56 Ȁ 14 to 63 Ȁ 15 mmHg ( P < 0.01, Wilcoxon signed rank test), in 3 months. Conclusion: These results suggest that addition of CO 2 immersion to standard care of critical limb ischemia in diabetic patients improves early postoperative outcome after vascular surgery.