BACKGROUND Improved methods of tissue diagnosis for obstruction at the hilum of the liver (porta hepatis) have contributed substantially to the preoperative diagnosis of cholangiocarcinoma. Endoscopic brushing during endoscopic retrograde cholangiopancreatography (ERCP), with sensitivity of 20% to 100%, is the preferred technique for obtaining accurate pathologic results. Extensive hepatic resection with curative intent as well as modern approaches to palliative treatment are based on definitive diagnosis. This is a study involving endosonography-guided, fine-needle aspiration (EUS-FNA) for cytodiagnosis of potentially operable hilar cholangiocarcinoma when brush cytology was negative or unavailable. METHODS Ten consecutive patients (7 men, 3 women; age 47 to 78 years, median 59 years) with bile duct strictures at the hepatic hilum, diagnosed by CT and/or ERCP, underwent EUS-FNA using linear echoendoscopes and 22-gauge needles. RESULTS Adequate material was obtained in nine patients. Cytology revealed cholangiocarcinoma in seven and hepatocellular carcinoma in one. One benign inflammatory lesion identified on cytology proved to be a false-negative finding by frozen section. Metastatic locoregional hilar lymph nodes were detected in two patients, and in one patient the celiac and para-aortic lymph nodes were aspirated to obtain tissue proof of distant metastasis. There were no complications. CONCLUSIONS When standard methods of tissue diagnosis are inconclusive, EUS-guided FNA may have a potential role in the diagnosis of primary cholangiocarcinoma of the hepatic hilum. As a new, minimally invasive approach, it proved to be technically feasible without significant risks.