Rhenium-188-hydroxyethylidine diphosphonate (188Re-HEDP) is a novel and attractive radiopharmaceutical that localizes in areas of osseous metastases and emits beta particles with energy sufficient to be therapeutically useful. The aim of this study is to evaluate the effectiveness of 188Re-HEDP in patients with lung cancer for the palliation of painful osseous metastases. Intravenous administration of activities ranging between 1.15 GBq (31 mCi) and 4.6 GBq (124 mCi) of 188Re-HEDP was given to each of 30 patients with painful osseous metastases from lung cancer. The patients were clinically followed at weekly intervals for the first 2 months, and monthly thereafter up to 1 year. Hematologic testing was performed before treatment and thereafter for 6 weeks. Pain response was scored by a four-point pain-rating scale as complete, marked, mild, and no response. Prompt and significant relief of bone pain occurred in 80% with no significant side-effects or hematopoietic toxicity. Forty-six percent (46%) of the patients discontinued analgesics after treatment. This clinical study indicated that 188Re-HEDP can offer significant pain palliation and is a useful radiopharmaceutical for treating painful osseous metastases from lung cancer.