Infection following hip arthroplasties can present a diagnostic challenge. No test is 100% sensitive and 100% specific; this prospective study was undertaken to evaluate the utility of FDG-PET imaging for diagnosing infected joint replacements. 24 hip joint replacements were studied prospectively and we have complete diagnoses with clinical signs and symptoms, laboratory tests, radiography, joint aspiration, radionuclide imaging including FDG-PET, and histopathologic examination. 11 of 24 prostheses were infected. The sensitivity and specificity of PET for detecting infection associated with prostheses were 64.3% and 64.7% respectively, in our study. FDG imaging is not useful in patients with suspected prosthetic infection as a screening test.