Two hundred and two patients with bone pain from metastatic cancer were treated with 40 microCi/kg of Sr-89. Patients were followed with pain diaries, records of medication taken, sleep patterns, serial bone scans and a Karnofsky Index. One hundred and thirty-seven patients with adequate followup survived at least 3 months, including 100 with prostate and 28 with breast carcinoma. Eighty of the 100 patients with prostate cancer responded, and 25 of the 28 breast cancer patients improved. Ten patients with prostate cancer and five with breast cancer became pain free. Little hematologic depression was noted. Sr-89 kinetic studies showed that strontium taken up in osteoblastic areas remained for 100 days. The tumor-to-marrow absorbed dose ratio was 10:1.