Aim: To evaluate the role of CHADS(2) and CHA(2)DS(2)-VASc scores in predicting the risk of ischemic stroke or transient ischemic attack (TIA) outcomes in patients with interatrial block (IAB) without a history of atrial fibrillation (AF). Methods: A retrospective study was conducted, including 1,046 non-anticoagulated inpatients (612 males, 434 females; mean age: 63 +/- 10 years) with IAB and without AF. IAB was defined as P-wave duration > 120 ms using a 12-lead electrocardiogram. CHADS(2) and CHA(2)DS(2)-VASc scores were retrospectively calculated. The primary outcomes evaluated were ischemic stroke or TIA. Results: During the mean follow-up period of 4.9 +/- 0.7 years, 55 (5.3%) patients had an ischemic stroke or TIA. Receiver operating characteristic (ROC) curve analysis showed that the CHADS(2) score [area under the curve (AUC), 0.638; 95% confidence interval (CI), 0.562-0.715; P = 0.001] and the CHA(2)DS(2)-VASc score (AUC, 0.671; 95% CI, 0.599-0.744; P<0.001) were predictive of ischemic strokes or TIA. Cut-off point analysis showed that a CHADS2 score = 3 (sensitivity = 0.455 and specificity = 0.747) and a CHA(2)DS(2)-VASc score = 4 (sensitivity = 0.564 and specificity= 0.700) provided the highest predictive value for ischemic stroke or TIA. The multivariate Cox regression analysis showed that CHADS2 [hazard ratio (HR), 1.442; 95% CI, 1.171-1.774; P = 0.001] and CHA(2)DS(2)-VASc (HR, 1.420; 95% CI, 1.203 -1.677; P < 0.001) scores were independently associated with ischemic stroke or TIA following adjustment for smoking, left atrial diameter, antiplatelet agents, angiotensin inhibitors, and statins. Conclusions: CHADS(2) and CHA(2)DS(2)-VASc scores may be predictors of risk of ischemic stroke or TIA in patients with IAB without AF.