Kristian Antonsen,1 Charlotte Vallentin Rosenstock,2 Lars Hyldborg Lundstrøm2 1Board of Directors, Copenhagen University Hospital, Bispebjerg and Frederiksberg Hospital, Capital Region of Denmark, Denmark; 2Department of Anesthesiology, Copenhagen University Hospital, Nordsjællands Hospital-Hillerød, Capital Region of Denmark, Denmark Aim of database: The aim of the Danish Anaesthesia Database (DAD) is the nationwide collection of data on all patients undergoing anesthesia. Collected data are used for quality assurance, quality development, and serve as a basis for research projects. Study population: The DAD was founded in 2004 as a part of Danish Clinical Registries (Regionernes Kliniske Kvalitetsudviklings Program [RKKP]). Patients undergoing general anesthesia, regional anesthesia with or without combined general anesthesia as well as patients under sedation are registered. Data are retrieved from public and private anesthesia clinics, single-centers as well as multihospital corporations across Denmark. In 2014 a total of 278,679 unique entries representing a national coverage of ~70% were recorded, data completeness is steadily increasing. Main variable: Records are aggregated for determining 13 defined quality indicators and eleven defined complications all covering the anesthetic process from the preoperative assessment through anesthesia and surgery until the end of the postoperative recovery period. Descriptive data: Registered variables include patients' individual social security number (assigned to all Danes) and both direct patient-related lifestyle factors enabling a quantification of patients' comorbidity as well as variables that are strictly related to the type, duration, and safety of the anesthesia. Data and specific data combinations can be extracted within each department in order to monitor patient treatment. In addition, an annual DAD report is a benchmark for departments nationwide. Conclusion: The DAD is covering the anesthetic process for the majority of patients undergoing anesthesia in Denmark. Data in the DAD are increasingly used for both quality and research projects. Keywords: anesthesia, quality indicators, complication, registries, epidemiology, registry-based research