The skeleton is a common site for metastases in patients with prostate and breast cancer. Beside analgesic therapy and external beam radiotherapy, the use of bone-seeking radiopharmaceuticals gives pain relief. Analogues of these pharmaceuticals are also applied in skeletal scintigraphy. They accumulate at the site of high osteoblast activity and in this way they exert a local favourable influence on metastases through their radiation (beta particles or conversion electrons). The bone-seeking radiopharmaceuticals include strontium-89 chloride and rhenium-186 hydroxyethylidenediphosphonate. The main adverse reaction that has been observed is myelosuppression.