Introduction: The Danish Heart Register (DHR) is a clinical database of invasive procedures within cardiology. Content: All providers of these procedures have been obliged to report to DHR since 2000. DHR is used to monitor the activity and quality of the procedures and serves as a data source for research. Validity and coverage: The coverage is high (>95%) but some variables have many missing. CONCLUSION: The combination of both cardiological and surgical data in this register is internationally unique and makes it possible to follow the patient from the invasive examination to treatment and by linkage to other registers to follow the prognosis.