Acute pancreatitis is a major adverse event of endoscopic retrograde cholangiopancreatography (ERCP). Rectal administration of non-steroidal anti-inflammatory drugs (NSAIDs) decreases the incidence of post-ERCP pancreatitis (PEP). Little is known about the combined effects of sublingual nitrate and NSAIDs. We performed a randomized trial to assess whether the combination of NSAIDs and sublingual nitrate is more effective than NSAIDs alone in preventing PEP.