Endoscopic retrograde cholangiopancreatography (ERCP) is a specialized endoscopic procedure to view the biliary and pancreatic ducts fluoroscopically. First introduced in the 1970s as a diagnostic tool, ERCP has since evolved primarily into a therapeutic modality and is today regarded as the premier tool for performing therapeutic interventions involving the biliary and pancreatic ductal systems. Relatively complex, ERCP requires advanced training. Although generally considered safe, it does carry a risk of significant complications, including pancreatitis; thus, the most important factor to mitigate complications is to ensure the presence of an appropriate indication for the procedure. This review addresses the indications (e.g., disorders of the major duodenal papilla, biliary diseases, and pancreatic diseases), contraindications, protocol, and complications of ERCP, as well as an overview of the tools available for ERCP procedures. Figures show ampullary adenomas, choledocholithiasis, Mirizzi syndrome, benign common bile duct stricture, primary sclerosing cholangitis, malignant biliary stricture, bile leak, type I and III choledochal cysts, chronic pancreatitis, pancreatic ductal disruption, classic fish-mouth appearance of the papilla in a patient with main duct intraductal papillary mucinous neoplasm, pancreas divisum, side-viewing duodenoscope used for ERCP, and selected tools of ERCP. Tables list the Rome III criteria, risk-stratifying patients for choledocholithiasis, diagnostic criteria for acute cholangitis, choledochal cyst classification, and the Cambridge classification system for chronic pancreatitis. This review contains 15 highly rendered figures, 5 tables, and 77 references.