OBJECTIVES: In this substudy of the ACUITY (Acute Catheterization and Urgent Intervention Triage strategY) trial, we investigated the relationship between chronic kidney disease (CKD) and clinical outcomes, and compared the safety and efficacy of bivalirudin monotherapy versus heparin plus a glycoprotein IIb/IIIa inhibitor (GPI). BACKGROUND: CKD is an important predictor of prognosis in the general population. The outcomes of patients with CKD and acute coronary syndromes (ACS) have not been well studied. METHODS: In the ACUITY study, 13,819 patients with moderate- and high-risk ACS undergoing an early, invasive strategy were randomly assigned to 1 of 3 antithrombin regimens: a heparin plus a GPI, bivalirudin plus a GPI, or bivalirudin monotherapy. CKD (creatinine clearance <60 ml/min) was present in 2,469 (19.1%) of 12,939 randomized patients with baseline creatinine clearance data. RESULTS: Patients with CKD had worse 30-day and 1-year clinical outcomes than those with normal renal function. There were no significant differences between bivalirudin monotherapy and heparin plus a GPI in rates of 30-day composite ischemia (11.1% vs. 9.4%, p = 0.27) and net clinical adverse outcomes (16.1% vs. 16.9%, p = 0.65). There was remarkably less major bleeding (6.2% vs. 9.8%, p = 0.008) at 30 days, but no significant difference in 1-year composite ischemia (22.0% vs. 18.9%, p = 0.10) or mortality (7.1% vs. 7.3%, p = 0.96). CONCLUSIONS: In patients with ACS, CKD is associated with higher 30-day and 1-year adverse event rates. Compared with heparin plus a GPI, the use of bivalirudin monotherapy in patients with CKD results in nonstatistically different ischemic outcomes, but significantly less 30-day major bleeding.