Abstract： Objective To prospectively evaluate the value of US,MSCT,EUS and MRI in the quantitative evaluation of the extent of pancreaticobiliary duct obstruction in pancreatic cancer.Methods Consecutive 68 patients with pancreatic carcinoma underwent US,MSCT,EUS and MRI before surgery.The diameter of extrahepatic bile duct and pancreatic duet were measured,and correlation analysis was performed with surgical specimens.Results Diameters of extrahepatic bile duct scaled by US.MSCT,EUS and MRI were(16.60±6.33)mm,(18.90±6.74)mm,(18.80±5.88)nun and(17.26±4.83)mm,and diameter measured from surgical specimens was(18.39±6.05)mm;the correlation among the four imaging examinations and the surgical evaluation were r=0.3839,P=0.1055;r=0.7113,P=0.0011; r=0.3759,P=0.0465;r=0.3376,P=0.2872,respectively. Kappa Values were 0.6285,0.7115,0.6661 and 0.7490,respectively.The diameter of pancreatic duct was(15.90±3.41)mm,(6.83 4-3.70)mm,(6.77±3.22)mm and(5.58±2.65)mm,and diameter measured from surgical specimens was(5.97±2.60)mm,the correlation among the four imaging examinations and the surgical evaluation were r=0.3584,P=0.2895;r=0.6148,P＜0.0001; r=0.7373,P＜0.0001;r=1.0746,P＜0.0001.Kappa values were 4.159,9.094,9.001 and 4.050.All of these parameters were in coherence with surgical findings.Condusions US could be used as the initial method in the assessment of extrahepatic and pancreatic duct obstruction.MRI and MSCT,combined with EUS if necessary,could be used to quantitatively evaluate the extent of pancreaticobiliary obstruction.