Background/Aims: Differentiation of benign obstructive jaundice from malignant obstructive jaundice still remains difficult, despite improvements in diagnostic modalities. The aim of this study is to evaluate the usefulness of red cell distribution width (RDW) in differentiating benign and malignant causes of obstructive jaundice. Methodology: One hundred and ninety four consecutive patients (101 malignant, 93 benign) with a history of obstructive jaundice were reviewed in the period between January 2008 and August 2009. Definition of biliary strictures was suggested by cholangiographic features and supported by brush cytology, fine needle aspiration (FNA) and the presence of mass or metastases by imaging and/or clinical follow-up. Patients were divided into two groups, benign and malignant, based on the discharge diagnosis. Results: The receiver operating characteristic analysis showed that a RDW of 14.8% was the best cut-off value for predicting a malignant biliary stricture with a sensitivity of 72% and a specificity of 69% (AUC=0.755, 95% CI=0.649-0.810). RDW was increased (>14.8%) in 31.6% of benign cases and 68.4% of malignancies. Depressed RDW levels (<14.8%) were found in 72.9% of benign cases and 27.1% of malignancies, which was statistically significant (p<0.001). Conclusions: Our results show that RDW is useful in the differentiation of benign from malignant causes of biliary obstruction when using an optimized cut-off value. In patients in whom biliary obstruction is suspected, an elevated RDW value may be a reliable additional predictor for differentiating the underlying etiology of biliary obstruction.