Background/Aims: Tissue biopsy from the biliary tree is difficult because of the focal and sclerotic or small annular nature, lower cellularity and well differentiated tumor. Biliary cytology is an effective tnethod of obtaining a tissue diagnosis for bile duct stricture, and thie diagnostic sensitivity of endoscopic brush cytology (EBC) is reported as between 40% and 70% for malignant bile duct strictures. In this study, we prospectively analyzed the diagnostic value of endoscopic brush cytology and aspiration bile cytology in patients with extrahepatic bile duct strictures. Methods: 30 patients with extrahepatic bile duct strictures diagnosed at endoscopic retrograde cholangiopancreatography underwent endoscopic brush cytology and aspiration bi]e cytology. 25 patients had malignant strictures and 5 patients had benign strictures, brushings were taken using a cytology brush(6Fr) or double lumen brush(8Fr) passed with a guide wire through the stricture. Results: The sensitivity and accuracy of brush cytology (60%; 15/25, 67%; 20/30) were significantly greater than bile cytology (20%; 5/25, 33%; 10/30). No false positive results were reported in brush cytology (specificity; 100%), but negative predictive value (33%; 5/15) was relatively low. There were no procedure related complications and the average sampling time was about five minutes. Conclusions: Endoscopic brush cytology is an effective, safe method of obtaining a tissue diagnosis for bile duct strictures, therefore EBC should be done routinely in bile duct strictures, but further prospective studies will be required to evaluate other new techniques such as endobiliary forceps biopsy or endoscopic fine needle aspiration or EBC with DNA flow cytometry because negative results do not exclude malignancy.(Korean J Gastroenterol 1996; 28: 832-844)