Sera from 40 patients (25 men, and 15 women) with clinical features compatible with the diagnosis of chronic Q fever were received. Total or partial clinical data were available. All of them had serological evidence of chronic Q fever (IgG class anti-phase I titer greater than 800). The final diagnosis was vascular infection in four cases (with two positive cultures for Coxiella burnetii), bone infection in two patients (one positive culture), chronic hepatitis in one patient, and endocarditis in 32. The last patient had an isolated fever with a chronic Q fever serologic profile. Among the 32 with endocarditis, valve replacement was performed in 59%, and valve cultures were positive in 14/18 patients. Twenty-nine of these patients had previously known valvulopathy; 23 were exposed to cattle, sheep or goats; and four had an immunocompromised situation. Ten patients died; two before any treatment, five of cardiac failure during or a few weeks after surgery, and three during the medical treatment. For antibiotic treatment, tetracycline alone was employed in seven cases. For the other patients, combined therapy including tetracycline and another drug (rifampin, fluoroquinolones, cotrimoxazole, or erythromycin) was initiated. Three patients were considered to be completely cured.