Background The gallstone prevalence in the western world is 10-20%. Most gallstones are silent, but symptoms and complications appear in 20-40%. The incidence of symptom development in patients with silent gallstones is 2-4% per year. The indication for surgical (including endoscopic) treatment of gallstones is symptoms of certain magnitude, and no contraindications. During the past three decades an intense technical development in imaging (ultrasound, computerised tomography and magnetic resonance imaging), endoscopic therapy, and surgery has taken place. The aim of this thesis is to scrutinize changes in management of complicated gallstone disease on a population-based level, using national register data. Have the new methods improved the treatment of acute pancreatitis, common bile duct stones and acute gallbladder disease? Methods Data is collected from National Patient Register (NPR) run by The Swedish National Board of Health and Welfare. NPR collects discharge data from every admission from every Swedish hospital. Mortality is calculated as standardised mortality ratio (SMR) using age-, gender-, and calendar year specific survival estimates. We have studied both general trends in admissions and treatment alternatives and outcomes in defined patient cohorts. Length of hospital stay, readmission, and mortality has been used as proxy indicators of the effectiveness of treatment strategies used. Results During the study period mortality in acute pancreatitis (SMR within 90 days of admission) improved and hospital stay for all patients with acute pancreatitis decreased. Cholecystectomy rate at or shortly after index stay for mild acute biliary pancreatitis increased from 14.5 % to 22.7 %. Of all patients with acute pancreatitis 68.4 % of the patients had no aetiological diagnosis in the register. The incidence of bile duct interventions increased 27.8% from 1988 through 2006. The favoured treatment of bile duct stones changed from open choledocholithectomy to endoscopic sphincterotomy with stone extraction during the same period. However, in 2006, still 19.6% of bile duct interventions for stones were performed as choledochotomy and in the great majority of these cases as open surgery. This indicates a continuing need of education in open bile duct surgery. Mean hospital stay for treatment of common bile duct stones decreased significantly (4.5 days) during the period studied. The mortality (SMR) diminished although without statistical significance during the time period, and there was no significant difference in SMR between choledochotomy and endoscopic sphincterotomy. For acute gallbladder disease a moderate increase of admissions occurred from 1988 through 2006. The relation between acute cholecystectomies versus all cholecystectomies did not change during this period. Of all patients admitted with acute gallbladder disease 32.3 % were cholecystectomised during their first hospital stay, whereas 20.3 % underwent elective cholecystectomy and 6.1 % emergency cholecystectomy within two years of first admission. 41.4 % of patients were not operated on for gallbladder disease within two years of first admission with this diagnosis. Mortality from first admission and 90 days onwards was elevated three-fold during the entire period without time trend, without statistical difference between age groups, and between patients who had cholecystectomy at first admission or later. Conclusion During the audit period treatment of acute pancreatitis improved. However, etiological classification and timing of cholecystectomy in mild acute biliary pancreatitis fell below accepted guidelines. Interventions on the common bile duct for gallstone disease increased significantly. Common bile duct clearance has been separated from cholecystectomy, and cholecystectomy often not done. Only one third of all patients with acute gallbladder disease underwent cholecystectomy at first admission. There is room for improvement in treatment of complicatedgallstone disease, and, gallstone surgeons still need good knowledge in open biliary surgery.