Coxiella burnetii was isolated from the valve material of two patients who underwent valvectomy because of progressive congestive heart failure due to endocarditis. In each case antibiotic therapy was administered for several months prior to valvectomy. Classical histopathological examination of the valves did not reveal an etiology. However, coxiella-like organisms were demonstrated in valvular material with Köster, Stamp, and Giemsa stains, and the organisms were grown in cell culture. Antibody titers were consistent with the diagnosis of chronic C. burnetii infection. This report illustrates the advantage of simple and fast staining techniques and cell culture for the demonstration and isolation of C. burnetii in the heart valve tissue of patients with Q fever endocarditis.