The purpose of this research study is to determine if indomethacin, an anti-inflammatory medication in a class of medications known at NSAIDs (non-steroidal anti-inflammatory drugs) can reduce the risk of pancreatitis after Endoscopic Retrograde Cholangio-Pancreatography (ERCP.) The hypothesis is that indomethacin decreases the incidence and severity of post-ERCP pancreatitis. Patients who are scheduled to undergo a ERCP will be enrolled. Following ERCP, patients will be randomized to receive a dose of indomethacin or placebo (an inactive substance) instilled into the duodenum via the biopsy channel of the duodenoscope. All patients will be observed for 4 hours following ERCP which is part of routine clinical practice. Patients with minimal pain will be discharged after this 4 hour observation period. All patients will have baseline serum amylase levels which are repeated 2 to 4 hours after the ERCP has been completed. Patients who have significant abdominal pain will be hospitalized and evaluated for pancreatitis. Patients discharged to home will be contacted by telephone the following day to ask them if they have had any complications of ERCP.