Infections, neoplasms, and collagen vascular diseases like many others are among the causes of fever of unknown origin with a varying frequency depending upon the age. Among infectious causes, infective endocarditis is reported as 0-8% in western countries and 0-3.8% in Turkey as the cause of fevers of unknown origin. Infective endocarditis is an infectious disease and is of great importance because of its high mortality and morbidity. It should be considered in the differential diagnosis in case of fever and cardiac murmur. In this report, 8 cases of infective endocarditis detected while investigating the etiology of fever of unknown origin are presented.