In a recent issue of CHEST (November 2010), Pisters et al1 published an interesting work that establishes a score to assess 1-year risk of major bleeding in patients with atrial fibrillation. In this article, kidney failure (defined as the presence of chronic dialysis or renal transplantation or serum creatinine ≥ 200 μmol/L) is identified as a risk factor for major bleeding. The “Discussion” section of the article stated that in the vast majority of patients with atrial fibrillation who require oral anticoagulation (CHADS2 [congestive heart failure, hypertension, age > 75 years, diabetes mellitus, previous stroke/transient ischemic attack (doubled)] index ≥ 2), the risk of bleeding outweighs the potential benefits of oral anticoagulation if the HAS-BLED (hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly [> 65 years], drugs/alcohol concomitantly) score exceeds the individual CHADS2 index. As such, a 75-year-old man with hypertension and renal failure would have a CHADS2 index of 2 and HAS-BLED score of 3, and the oral anticoagulant treatment should be discouraged. We believe that this recommendation does not take into account the impact of renal failure on thromboembolism risk in patients with atrial fibrillation. In all trials in which the benefit of oral anticoagulant in the prevention of thromboembolism in atrial fibrillation was established, the patients with end-stage renal failure were excluded, and in the European Heart Survey on atrial fibrillation, renal failure was not evaluated as a risk factor for thromboembolism.2 However, in the ATRIA (Anticoagulation and Risk Factors in Atrial Fibrillation) study, chronic kidney disease increased the risk of thromboembolism in atrial fibrillation independently of other risk factors3; in addition to this, studies carried out in our institution show that the patients with end-stage renal disease and atrial fibrillation have a very high rate of thromboembolism.4,5 We believe that this excellent risk score should have considered that although renal failure can increase the bleeding risk, it can also increase the risk of thromboembolism.