131 patients with osteolytic metastases from breast cancer were randomised to receive long-term oral treatment with aminohydroxy-propylidene-bisphosphonate (APD), 300 mg daily (n = 70), or to act as controls (n = 61) in a multicentre trial. Specific antitumour therapy was at the discretion of the clinician and variable. An interim analysis was made after a median follow-up of 13 months in the APD group and 14 months in the controls. There was a significant reduction in pathological fractures and severe bone pain in the APD group, and hypercalcaemia was prevented. Consequently the necessity for radiotherapy for skeletal complications was more than halved; the number of systemic therapy changes was also reduced. Gastrointestinal side-effects of APD led to a drop-out of 8% of patients. Oral supportive APD therapy is simple and convenient, and significantly reduced skeletal morbidity in advanced breast cancer.