Background: Endoscopic retrograde cholangiography (ERC) is technically challenging in liver transplant patients with Roux-en-Y biliary anastomosis. The optimal endoscope for such cases remains unknown. Objective: Compare efficacy and safety of performing ERC in liver transplant patients with Roux-en-Y biliary anastomosis by using an adult colonoscope (AC), a pediatric colonoscope (PC), and a single-balloon enteroscope (SBE). Design: Retrospective chart review. Setting: Tertiary-care referral center. Patients: Liver transplant patients with Roux-en-Y biliary anastomoses. Intervention: ERC with AC, PC, and SBE. Main Outcome Measurements: Rates of reaching the afferent limb and biliary anastomosis; rates of cannulation; rates of diagnostic, therapeutic, and procedural success; and number of adverse events. Results: Ninety patients underwent 199 ERCs from 2002 to 2012; 86 with an AC, 55 with a PC, and 58 with an SBE. Biliary cannulation and diagnostic, therapeutic, and procedural success rates were all significantly higher with an SBE than with a PC. Among patients undergoing the initial ERC, no statistical difference was found among SBE, the PC, and an AC. However, the rate of procedural success with SBE during initial ERC over the last 4 years has increased. Of 25 total failures with ACs, exchange for SBEs resulted in procedural success in 4 of 4 attempts. Of 22 failures with a PC, exchange for an SBE resulted in success in 3 of 4 cases. Of 4 failures with SBE exchange in 6 cases (4 to AC, 2 to PC), SBE resulted in success in only 1. No adverse events occurred directly related to type of endoscope. Limitations: Retrospective study, single center, lack of standardized approach to selection of endoscopes, uncontrolled variables (general anesthesia, learning curve). Conclusion: In liver transplant patients with Roux-en-Y anatomy, rates of biliary cannulation, therapeutic success, and procedural success are higher with use of an SBE than with a PC and tend to be higher compared with use of an AC among the overall cohort. Use of an SBE and procedural success rates with SBEs have increased over the last 4 years. Failed cases with either an AC or PC can be completed if exchanged for an SBE.