BACKGROUND/AIMS: It is controversial to use serum cartinoembryonic antigen (CEA), serum CA19-9 bile CEA, and bile CA19-9 in diagnosing malignant pancreaticobiliary diseases. The aim of this study was to determine whether a short-term biliary drainage affects the values of serum CEA, serum CA19-9, bile CEA, and bile CA19-9 and thus, improves diagnostic values. METHODS: Thirteen patients with benign causes of obstructive jaundice and/or acute cholangitis and 24 patients with malig nant causes were examined. All patients underwent endoscopic or percutaneous biliary drainage. Serum and bile samples were obtained at the time of biliary drainage procedure and at 2 and 7 day of post-drainage. Then, the values of CEA and CA19-9 were measured. RESULTS: Biliary drainage did not change serum CEA in benign and malignant diseases. The specificity and positive predictive value (PPV) of serum CEA were increased after drainage, whereas its sensitivity, negative predictive value (NPV), and accuracy were decreased. Serum CA19-9 was significantly decreased at 7 days of post-drainage in benign diseases (p=0.0018). The specificity, PPV, NPV, and accuracy of serum CA19-9 increased after drainage, whereas its sensitivity was decreased. The values of bile CEA and CA19-9 were not affected by biliary drainage and showed no difference between benign and malignant diseases. CONCLUSIONS: Biliary drainage affects the diagnostic values of serum CEA and CA19-9. Bile CEA and CA19-9 have no diagnostic roles.