Metastatic bone disease was evaluated in 380 consecutive patients at the time of first metastasis of breast cancer. Studies included radiographic examination, radionuclide examination, and bone marrow biopsy. Radiographs of the skeleton demonstrated metastases in 120 patients (32%), and in 40 of these patients (13%) the bone was the only site of metastases. The diagnostic efficiency was 82% for bone scanning, 80% for pain evaluation, 59% for s-calcium analyses, and 77% for s-alkaline phosphatase analyses. Bone scanning is an effective method to exclude metastatic bone disease (sensitivity: 96%). A positive scan, however, requires radiologic confirmation (specificity: 66%). Bone scanning of the skeleton should be the initial staging procedure in all patients with recurrent breast cancer with no clinical or biochemical signs of bone metastases. Bilateral posterior iliac crest bone marrow aspirations and bone biopsies were positive in 82 out of the 320 patients who underwent biopsy. The frequency of positive bone marrow biopsy was significantly correlated with both the site of radiographic metastases and with the total number of involved bone regions. Routine bone marrow biopsies are indicated in patients with a positive bone scan, but a negative x-ray examination. In these cases biopsies should be performed bilaterally.