A case of endocarditis caused by Coxiella burnetii in a patient with an aortic Starr-Edwards prosthesis is described. The diagnosis was made by detecting high titres of antibody against Coxiella burnetii phase I antigens. After 15 weeks of chemotherapy with tetracycline and cotrimoxazole, aortic prosthetic valve replacement was carried out because of haemodynamic deterioration and he died 4 days later. The histologic picture of the excised valve was consistent with endocarditis. Coxiella burnetii should be considered in the differential diagnosis of culture-negative endocarditis in our country, especially when the patient has not receiving antibiotic treatment in the last 2 weeks.