Q fever is caused by the rickettsia Coxiella burnetti, an obligate intracellular bacterium acquired by inhalation of infected dust from subclinically infected animals. Q fever may be acute or chronic; the chronic form mostly presents as endocarditis. Immunocompromised states and underlying heart disease are the most important risk factors. Usually the symptoms of Q fever endocarditis are nonspecific and diagnosis is often established very late. New criteria for diagnosis include a single blood culture positive for Coxiella burnetti, positive Q fever serology and characteristic echocardiographic studies. We describe a 49-year-old man with bicuspid aortic valve admitted with fever, weight loss and a new heart murmur. The diagnosis of Q fever endocarditis was established by positive Q fever serology, and an echocardiogram showing vegetations and valvular dysfunction. This case suggests that Q fever endocarditis should be considered in patients with "sterile" endocarditis.