Background : In a retrospective analysis of a prospective single center registry we compared the use of bivalirudin, unfractionated heparin (UFH) monotherapy, UFH + abciximab in 1240 consecutive patients with acute coronary syndrome (ACS) undergoing stent implantation. ; Results : Bivalirudin was associated with tendentially reduced in-hospital minor or major bleeding rates compared to UFH monotherapy (5.9 % vs. 9.4 % adjusted odds ratio (OR) 0.82, 95 % confidence interval CI 0.45–1.51, p = 0.53) and compared to the pooled UFH group (5.9 % vs. 11.9 %, adjusted OR 0.62, 95 % CI 0.36–1.08, p = 0.09) but with significantly lower bleeding hazards compared to UFH + abciximab (5.9 % vs. 16 %, adjusted OR 0.41, 95 % CI 0.22–0.78, p