Objective: To investigate the changes of plasma endothelin-1 (ET-1) and NO before and after balloon angioplasty in patients with atherosclerotic occlusive disease (ASO) below the knee and its clinical significance. Method: A total of 38 patients with ASO below the knee, who underwent balloon angioplasty in department of vascular surgery of Tsitsihar First Hospital from February 2013 to February 2014, were selected. The changes of plasma ET-1 and NO levels before operation and 6 hours, 24 hours, 1 week, 1 month and 3 months after operation were compared. All the patients were checked with CT angiography(CTA) 1 month and 3 months after operation respectively to observed whether vascular restenosis occurred or not, and the relationship between vascular restenosis and plasma ET-1 and NO levels was analyzed. Results: Compared with before operation, the plasma ET-1 levels 6 hours after operation increased significantly and decreased slightly from 24 hours to 1 week after operation in all the patients, but still kept at a high level, while the changes of NO was opposite to plasma ET-1.There were 33 patients without vascular restenosis after checked with CTA, the plasma ET-1 and NO levels resumed to preoperative level 1 month after operation and kept till 3 months after operation; however, there were 5 patients with vascular restenosis, the plasma ET-1 level kept at high level from 1 month to 3 months after operation, and the changes of NO was opposite to plasma ET-1 level. Conclusion: The plasma ET-1 and NO levels was related with vascular restenosis after balloon angioplasty in patients with ASO below the knee. [ABSTRACT FROM AUTHOR]