Background and Aims: Despite advances in endoscopic techniques for sampling bile duct strictures, the diagnosis of cholangiocarcinoma remains a challenge. The purpose of this study was to evaluate the yield of EUS-FNA and its impact on patient management for patients with suspected cholangiocarcinoma. Methods: All patients undergoing EUS for the evaluation of suspected malignant biliary strictures were prospectively evaluated over a 23-month period. A single gastroenterologist performed all EUS-FNAs in the presence of a cytopathologist. Reference standard for final diagnosis included surgery, death from disease, and clinical and/or imaging follow-up. Results: Twenty-eight patients (mean age 67 years [SD ± 11], 72% male) were evaluated. Most patients (91%) presented with obstructive jaundice, and all except 1 had nondiagnostic sampling of the biliary lesions either at ERCP (88%), percutaneous transhepatic cholangiogram (n = 2), and/or computed tomography-guided biopsy (n = 1). Sixty-seven percent (14/21) had no definitive mass seen on prior abdominal imaging studies. The mean tumor size by EUS was 19 mm × 16 mm with a median number of passes to diagnosis of 3 (range 1-7). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 86%, 100%, 100%, 57%, and 88%, respectively. EUS-FNA had a positive impact on patient management in 84% of patients: preventing surgery for tissue diagnosis in patients with inoperable disease (n = 10), facilitating surgery in patients with unidentifiable cancer by other modalities (n = 8), and avoiding surgery in benign disease (n = 4). Conclusions: Given the apparent accuracy and safety of EUS with FNA for imaging bile duct mass lesions and for obtaining a tissue diagnosis in patients with suspected cholangiocarcinoma, this technology may represent a new approach to diagnosis especially when other methods fail. The ability to obtain a definite diagnosis has a significant impact on patient management. © 2004 by the American Gastroenterological Association.