It is well known that increased concentrations of CA 19-9 can be found in benign disease of the liver, pancreas and biliary tract, especially in cases with gallstone disease with cholangitis. The aim of this study was to investigate the relation of CA 19-9 with the number and size of the stones, cholangitis and biliary obstruction in patients with choledocholithiasis. Methods: Seventy patients with radiologically proven choledocholithiasis were studied. Endoscopic retrograde cholangiopancreatography, sphincterotomy and stone extraction were applied to all patients. In each case, the parameters recorded included the levels of CA 19-9 and other laboratory tests before and after endoscopic retrograde cholangiopancreatography and the results of imaging techniques and immunoserologic tests. The correlations of these parameters were determined by SPSS 17 package program for statistical analysis. Results: Elevation of CA 19-9 was found in 32 patients (46%), while 8 patients (11%) had extraordinarily high levels (>1000 U/ml). CA 19-9 levels were correlated with serum alkaline phosphatase (r=0.5, p<0.01), gamma glutamyl transpeptidase (r=0.5, p<0.01) and bilirubin (r=0.4, p<0.01) levels but not with aspartate aminotransferase or alanine aminotransferase levels. There was also no association between serum CA 19-9 levels and the number and size of stones. Six patients had cholangitis. CA 19-9 levels were found higher in patients with cholangitis than others (100% vs. 41%, p<0.01) as well as alkaline phosphatase, gamma glutamyl transpeptidase and bilirubin levels. After stone extraction, CA 19-9 levels started to decrease and reached normal values 1-28 days later. Conclusion: In conclusion, CA 19-9 levels are associated with biliary obstruction and cholangitis but not with the number and size of stones in patients with choledocholithiasis.