A considerable fraction of first metastases in breast cancer patients are found in the skeletal system. Consequently, to improve the probability of detecting bone lesions, protocols of the National Surgical Adjuvant Breast and Bowel Project (NSABP) have required radionuclide scans every six months for the first three postoperative years and yearly thereafter. The present study was conducted to evaluate the worth of 7984 bone scans performed prior to documentation of first treatment failure on 2 697 stage II (positive node) patients entered into NSABP clinical trial B-09. At the time of evaluation, there were 779 patients with a treatment failure, 163 (20.9%) of whom had their recurrence limited to bone. At most, 52 (0.6%) of the total number of screening scans were efficacious in detecting lesions in asymptomatic patients. As a result of this minimal benefit from routine scans, it was recommended that they be conducted less frequently. In presently ongoing NSABP studies, asymptomatic patients having tumors with positive axillary nodes receive scans at yearly intervals for the first three years. Future NSABP trials will require follow-up bone scans only as indicated by symptoms.