Abnormal activity around the prosthesis on radionuclide bone scans has been described as effective for identifying prosthesis loosening in cemented total hip replacement. But, there are no criteria for the radiographic or radionuclide bone scan features that indicate loosening and infection in uncemented total hip replacement. The study was intended to determine the findings of radionuclide scans in asymptomatic uncmented total hip replacement following administration of technetium 99m methylene diphosphonate. Five areas of the prosthesis were evaluated. The bone scan changes of 85 cases in 45 asymptomatic patients were reviewed, and the following results were obtained. 1. Uptake on bone scans were highest at two to three months after surgery, and then gradually decreased. Most of the patients had normal uptake approximately 10 months after surgery. 2. The greater trochanter (5 cases), lateral portion of the stem (2 cases), prosthesis hip (6 cases), medial portion of the stem (1 cases), and lessor trochanter (6 cases) showed abnormally increased activity persisted until 12 months that need long term follow-up.