During a period of 3.5 years, endocarditis was suspected in 151 patients admitted to Rigshospitalet. 140 were available for this study. In 59 of the 140 patients, the diagnosis was confirmed, and 36 had positive blood cultures. Echocardiographic findings compatible with the diagnosis were present in 92% of the 59 cases. The most common causes of endocarditis were Staphylococcus aureus and viridans streptococci. Patients with endocarditis caused by S. aureus had significantly (p = 0.002) more embolic episodes compared to patients having endocarditis caused by the viridans streptococci. The diagnosis was established at a mean of 3–4 weeks after the onset of symptoms and 2 weeks after admission to hospital. In order to minimize diagnostic delay, the following aspects may be important: (1) earlier detection of endocarditis among physicians examining patients at risk; (2) educating patients with cardiac disease and cardiac valve prosthesis; (3) earlier antibiotic therapy, and (4) developing further diagnostics for endocarditis.