Phosphorus-32, employed as the orthophosphate or polyphosphate, can reduce or relieve the pain of osteoblastic metastases without serious hematologic toxicity, especially if used as a single injection. Uptake of this beta-emitter by osteoblastic-reactive bone and possibly by tumor and other cells can lead to pain reduction and often to cell killing. Efficacy has been demonstrated for the treatment of pain in 84% of 322 breast cancer patients and 77% of 444 prostate cancer patients found in a review of the literature. These results match those of the newer radiopharmaceuticals currently under investigation.