The purpose of this study was to evaluate the spectrum of plain radiographic findings in patients with septic hip prostheses.Radiographs of 20 confirmed infected hip prostheses were examined for the presence or absence of lucency, type of lucency (focal or nonfocal), rapidity of radiographic change, periostitis, subsidence, and cement fracture.Findings were normal in 10 prostheses, but nonfocal lucencies mimicking mechanical loosening were seen in four cases. Two cases showed focal bone loss, indistinguishable from aggressive granulomatosis. A variety of findings, including subsidence and periostitis, were seen in the remaining four prostheses.Plain radiographs of septic hip prostheses often show normal findings but can show focal bone loss that mimics aggressive granulomatosis.