Sodium etidronate is a diphosphonate compound that inhibits bone resorption and mineralization. The drug has been reported to be highly effective for the palliation of painful bone metastasis from prostatic cancer. Fifty-seven patients were entered into a randomized, prospective, double-blind, placebo-controlled study of sodium etidronate. All patients had hormone refractory metastatic prostatic cancer and bone pain requiring analgesics. No difference was seen in the symptomatic response rate or analgesic requirement between patients treated with sodium etidronate and placebo. With the dose scheme used in this study sodium etidronate was ineffective for palliation of bone pain from prostatic cancer.