Abstract BACKGROUND: Comprehensive, population-based data on ERCP use over the last 30 years in North America are lacking. OBJECTIVE: To establish crude and age-adjusted population-based rates of ERCP, evaluate for changing indications for ERCP, and evaluate for interactions between cholecystectomy technique and ERCP use from 1984 to 2009. DESIGN: Retrospective, comprehensive, population-based study. SETTING: All inpatient and outpatient ERCPs and cholecystectomies in Manitoba, Canada from 1984 to 2009. PATIENTS: All residents of Manitoba, Canada with a history of ERCP and/or cholecystectomy. INTERVENTION: None. MAIN OUTCOME MEASUREMENTS: Yearly crude and age-adjusted rates of ERCP (diagnostic and therapeutic) and cholecystectomy (open, laparoscopic, and with open bile duct exploration), and patient and/or procedure demographics. RESULTS: The rate of ERCP/10,000 people increased from 7.70 (1984) to 13.86/10,000 (2009) (P = .001). Diagnostic ERCP declined from 7.28/10,000 (1984) to 1.11/10,000 (2009), and therapeutic ERCP increased from 0.42/10,000 (1984) to 12.75/10,000 (2009) (P < .001). ERCPs were more common in women (62%) and in older populations (60-79 years, >80 years), with rates of therapeutic ERCP reaching 62.58/10,000 in the elderly. The primary indication for ERCP has changed over time, with biliary indications increasing from 50.3% to 67.3% and pancreatic indications decreasing from 18.3% to 8.1% (P < .05). The rate of therapeutic ERCP increased during the transition from open to laparoscopic cholecystectomy (1991-1994), whereas open bile duct exploration (OBDE) decreased from 2.0 to 0.18/10,000 (P < .001). LIMITATIONS: Retrospective analysis, administrative data. CONCLUSION: ERCP use increased steadily from 1984 to 2009, and changed from a diagnostic modality to a therapeutic one. Changes in cholecystectomy technique may have influenced therapeutic ERCP use and likewise, the availability of therapeutic ERCP has decreased the need for OBDE.