The most frequent clinical presentation of chronic Q fever is endocarditis, although infections of aneurysms and vascular prostheses have also been described. We report seven new cases of Coxiella burnetii infection of aneurysms or vascular grafts. We also review the literature and compare our cases with the six previously reported cases. This study demonstrated the lack of specific symptoms associated with this disease. Moreover, prospectively, in an attempt to reevaluate the incidence of Q fever-associated vascular infection, we systematically searched for C. burnetii infections in 163 patients with aortic aneurysms or vascular grafts who underwent vascular surgery. Microbiological testing included standard culture, Q fever serology, cell culture, and polymerase chain reaction amplification of C. burnetii DNA from biopsy specimens of aneurysms or vascular grafts. A microorganism was isolated from 25 patients, including C. burnetii in two cases; both of these patients had serological titers consistent with chronic Q fever. Both patients had nonspecific clinical features, and thus their infections would have probably remained undiagnosed without our systematic testing. Therefore, since the incidence of C. burnetii vascular infection is probably underestimated, we suggest that C. burnetii serology be routinely carried out in cases of unexplained febrile illness, pain, or weight loss in patients with a history of underlying vascular disease.