The role of aspiration of the hip joint before revision of a total hip arthroplasty remains controversial. To address this issue, we reviewed the results of 270 consecutive hips in which aspiration had been attempted before revision procedures that were performed between 1980 and 1988. All hips had intraoperative findings and clinical follow-up of at least two years to confirm the presence or absence of infection. Only six (2 per cent) of the 270 hips were determined to be infected. Aspiration had been attempted in all six hips, but fluid could be obtained from only four. All six hips also had clinical or radiographic signs, or both, of infection, including increasing pain within three years after the arthroplasty (four hips), inability of the patient to attain pain-free status after the original procedure (four hips), radiographic findings compatible with infection (six hips), and a positive finding on culture of a specimen obtained from a previous aspiration (two hips). Because of these factors, aspiration was attempted a second time in four of the six hips and a third time in three of the four. The four hips from which fluid could be obtained had a total of ten successful aspirations; the cultures of specimens obtained from six of these procedures were positive and those from four were negative. The appearance of the capsular tissue at the time of the operation suggested infection in five of the six infected hips. Histological sections were positive for inflammation in all six: there was acute inflammation only in one, chronic inflammation only in two, and acute and chronic inflammation in three. No organisms were seen on gram stains of specimens from any of the six infected hips. Of the 254 hips that did not have an infection and had been aspirated successfully, thirty-two (13 per cent) had a false-positive result on culture of a specimen of the aspiration fluid. Only two (6 per cent) of the thirty-four hips that had a positive result on culture of fluid from the initial aspiration had a true-positive result. No hip had a true-positive result on culture of fluid that had been aspirated preoperatively without also having clinical and radiographic evidence of infection. On the basis of these findings, we recommend that aspiration be performed in selected patients rather than routinely. It also should be performed only if a detailed clinical history suggests infection or if radiographs demonstrate focal lysis, aggressive non-focal lysis, or periostitis.