We retrospectively reviewed pretreatment levels of serum prostate specific antigen (PSA) in 138 newly diagnosed, untreated patients with prostate adenocarcinoma to evaluate the usefulness of serum PSA levels to predict results of radionuclide bone scans. All of the 24 patients with serum PSA levels above 200 ng/ml showed positive bone scans whereas those with serum PSA levels below 10 ng/ml included only three cases (3/51, 5.1%) positive for bone metastasis. All of the three had poorly differentiated adenocarcinoma of the prostate. In conclusion, bone scans may not be necessary in the cases with serum PSA levels less than 10 ng/ml except for those with poorly differentiated adenocarcinoma.