Background: Endoscopic ultrasound (EUS) may have a major diagnostic value in detecting etiologies of dilated common bile duct (CBD) undetected by other non-invasive modalities. Objectives: This study aimed to evaluate the diagnostic role of endoscopic ultrasonography in dilated common bile duct unexplained by Magnetic resonance cholangiopancreatography (MRCP). Methods: This study was conducted on 50 patients attending to the endoscopic ultrasound unit of the Hepatology, Gastroenterology and Infectious disease Department, Benha University Hospital and Endemic Medicine Department, Kasr AL Ainy Hospital presented with unexplained common bile duct dilatation. Every patient underwent TUS, MRCP and EUS. Results:By EUS examination pancreatic head mass was detected among 32% of cases, Pancreatic uncinate process mass in 16% of cases, chronic pancreatitis in 44%, TB pancreatitis in 2%, pancreatic duct dilatation in 40%, pancreatic body cyst in 4%and pancreatic divisum in 2% of cases, CBD dilatation in 100%, CBD stone detected in 20% of cases and CBD distal mass in 8%, ampullary mass in 10%, LN in 70% and GB stone in 20%. There were statistically significant differences between EUS and MRCP regarding detection of Pancreatic head mass, pancreatic uncinate process mass, chronic pancreatitis, small CBD stone (p=0.000, p=0.008, p=0.000, p=0.002) respectively. No statistically significant difference between them regarding detection of TB pancreatitis, pancreatic body cyst, pancreatic divisum, small CBD distal mass and ampullary mass (p=1, p=0.5, p=1, p=0.125, p=0.63) respectively.