Late infection after arthroplasty is a rare, but one of the most serious problems complicating total joint replacement. Prosthetic infections caused by Brucella spp. are rarely described in the literature. In addition, the diagnosis of the disease is frequently difficult because of the slowly growing and fastidious nature of the bacterium. In recent years, blood culture systems have been introduced into clinical practice, and it has been demonstrated that this system may be a convenient tool for the culture of Brucellae from synovial fluid of patients with arthritis The patient who underwent a total joint replacement 4 years ago presented initially with symptoms suggestive of prosthetic knee infection. Brucellar monoarthritis of the knee was detected with the culture of the synovial fluid with blood culture system while no growth was detected on the conventional blood agar and chocolate agar plates. In conclusion, we emphasize the fact that Brucella infection of prosthetic joints should be considered in the differential diagnosis of prosthetic joint infection especially in endemic areas, and the diagnosis of Brucella arthritis may be underestimated when inappropriate culture media are used. ©2008, Firat University, Medical Faculty.