Ten patients with disseminated bone metastases, nine from prostatic and one from renal cell carcinoma, were treated with intravenous strontium-89. Half the patients experienced significant improvement in pain control and increased general well-being for an average of 14 weeks. Sequential radiophosphate bone scanning showed decreased activity in lesions present at the time of therapy, with subsequent remineralization of the metastases on radiographs. Some patients showed simultaneous reduction in alkaline and acid phosphatase levels. These objective findings prove a physiologic basis for the clinical improvement. Treatments, however, did not prevent progression at initially uninvolved sites, particularly in the extremities.