After a baseline symptom and laboratory assessment, 24 patients with metastatic bone disease and pain were randomized to receive either a 4-hr intravenous infusion of 2-dichloromethylene bisphosphonate (Cl2MDP), 600 mg in 500 mL of normal saline, or a 4-hr placebo infusion, 500 mL of normal saline. The administration was double blind. After 1 wk, the assessment was repeated and the patients were crossed over to the alternate treatment. After 1 more wk, a final assessment and blinded choice by the patient and investigator took place. Of the 21 evaluable patients, 12 (57%) chose the Cl2MDP and 4 (19%) chose the placebo; 5 (24%) patients did not have a specific preference (p = NS). The investigator chose the Cl2MDP in 14 (67%) cases, placebo in 6 (29%) cases and was unable to discern a difference in 1 (5%) case (p less than 0.05). The patients and investigator made similar selections in 16 (76%) instances. On the visual analogue scale assessments, a significant decrease in pain scores was observed following the Cl2MDP infusion (p less than 0.01) and an increase in activity scores was also demonstrated (p less than 0.01). No significant difference in the daily oral morphine equivalent analgesic requirement was demonstrated for either arm. No difference in clinical and laboratory parameters of toxicity was evident between the placebo and Cl2MDP arms of the trial. Our preliminary findings suggest that Cl2MDP is safe, and has analgesic properties that may prove to be useful in the management of metastatic bone pain.