Radioactive strontium chloride (89Sr) was administered for pain relief in 6 patients with bone metastases (4 prostate cancer and 2 breast cancer patients). Out of 6 patients, 2 showed apparent relief of bone pain and improvement of QOL, and 3 showed slight relief of the pain with or without improvement of QOL; that is, 83% was effective. Side effects were seen in 2 patients; transient deterioration of bone pain in one patient and bone marrow suppression in the other patient. The patient who showed bone marrow suppression had rather more lesions of bone metastasis (diffuse metastasis) and least urinary excretion of the radioactivity. Urinary excretion for 2 days varied 5 to 40% of the administered dose and was less in the patients with more metastatic lesions.