Résumé : Background: The feasibility of single-operator cholangioscopy (SOC) for biliary diagnostic and therapeutic procedures was previously reported. Objective: To confirm the utility of SOC in more widespread clinical use. Design: Prospective clinical cohort study. Setting: Fifteen endoscopy referral centers in the United States and Europe. Patients: Two hundred ninety-seven patients requiring evaluation of bile duct disease or biliary stone therapy. Interventions: SOC examination and, as indicated, SOC-directed stone therapy or forceps biopsy. Main Outcome Measurements: Procedural success defined as ability to (1) visualize target lesions and, if indicated, collect biopsy specimens adequate for histological evaluation or (2) visualize biliary stones and initiate fragmentation and removal. Results: The overall procedure success rate was 89% (95% CI, 84%-92%). Adequate tissue for histological examination was secured in 88% of 140 patients who underwent biopsy. Overall sensitivity in diagnosing malignancy was 78% for SOC visual impression and 49% for SOC-directed biopsy. Sensitivity was higher (84% and 66%, respectively) for intrinsic bile duct malignancies. Diagnostic SOC procedures altered clinical management in 64% of patients. Procedure success was achieved in 92% of 66 patients with stones and complete stone clearance during the study SOC session in 71%. The incidence of serious procedure-related adverse events was 7.5% for diagnostic SOC and 6.1% for SOC-directed stone therapy. Limitations: The study was observational in design with no control group. Conclusions: Evaluation of bile duct disease and biliary stone therapy can be safely performed with a high success rate by using the SOC system. © 2011 American Society for Gastrointestinal Endoscopy.