In the Western world, gallstone disease accounts for approximately half of the cases of acute pancreatitis. The benefit of therapeutic endoscopic retrograde cholangiopancreatography (ERCP) has been clearly proven for this disease. On the basis of history, laboratory, and noninvasive imaging studies, about 10-30% of patients with acute pancreatitis have no apparent aetiology. This is critical because it limits the optimal therapeutic management and the prevention of recurrence. Endoscopic ultrasound (EUS) has emerged as an important procedure to clarify the aetiology of acute pancreatitis. After extensive investigation that included EUS, 8-20% of episodes remained idiopathic. Moreover, EUS carried minimal risk when compared to ERCP. The present short review attempts to update on the indications for the employment of EUS in the diagnosis of biliary stones as well as in the clarification of aetiology in the case of unexplained pancreatitis.