The medical records of 82 patients with breast cancer with bone-only metastases were reviewed. According to the distribution of the metastases by bone scan at the time they were first documented, the patients were divided into three groups: Group A (patients who had bone metastases exclusively cranial to the lumbosacral junction), Group B (patients who had bone metastases exclusively caudal to the junction), and Group C (patients who had bone metastases both cranial and caudal to the junction). Group A had a significantly higher visceral metastases-free rate than Groups B or C. Serial bone scans and radiographs of Group A patients revealed that bone lesions cranial to the junction rarely developed into visceral metastases and that bone lesions extending caudal to the junction frequently developed into visceral metastases. These results indicate that the presence of bone metastases caudal to the lumbosacral junction is predictive of visceral metastases.