My experience with clinical epidemiology and goes 25 years back when I entered cardiology. Following a number of successful smaller studies I conducted a multicenter interventional study of ACE inhibitors in myocardial infarction published in The New England Journal of medicine along with Lars Køber. This successful study led to further interventional studies. My work with epidemiology was primarily initiated with databases from these studies which also included data from consecutive patients screened from the studies. This was further expanded with participation at the steering committee level with international studies in which I have participated in more than 10. In 2002 I took up the subject of register based research because multiple register were provided at that time for research within a research environment in Statistics Denmark which holds multiple nationwide databases. Since then the main focus of my research has been register based studies and controlled clinical trials in cardiology.