Backgrounds: ClotinabTM is a biosimilar product of abciximab (Reopro짰), chimerical human monoclonal antibody binding to glycoprotein IIb/IIIa receptor. This single center, retrospective study was performed to compare the efficacy and safety of abciximab and ClotinabTM in high-thrombotic risk patients. Methods: From 2006 May to 2011 July, two hundred and fifty patients have gotten an intracoronary injection of abciximab (40 patients in abciximab group, from 2006 May to 2009 August, and 210 patients in ClotinabTM group, from 2009 September to 2011 July) due to STEMI, NSTEMI, and evidence of intracoronary thrombus during PCI (percutaneous coronary intervention) by physician���s discretion. Results: Baseline characteristics of patients were not different, except more hypertension in ClotinabTM group and longer stenosis of coronary artery in abciximab group, respectively. ClotinabTM group required more transfusion due to major bleedings. There were no differences in efficacies between two groups in terms of acute and subacute stent thrombosis, post-PCI TIMI flow, 1 month all cause mortality and MACE, however. Conclusions: ClotinabTM had a comparable effects compared to abciximab until 1 month. The bleeding risk was higher in ClotinabTM group, however. Large prospective and randomized trials are required to validate these findings.