Bisphosphonates have marked affinity for bone that makes them useful in both the treatment and imaging of bone lesions. Bone scintigraphy is very sensitive for the detection of bone metastases, which can cause life-threatening hypercalcemia requiring emergency treatment. This prospective study was done to determine whether intravenous administration of pamidronate, a second-generation bisphosphonate used to treat hypercalcemia, affects the affinity of the radiopharmaceutical 99m technetium-labeled hydroxymethylene bisphosphonate (99mTc-HMDP) for bone and bone lesions. Six patients with metastatic bone disease and five with Paget's disease of bone had a 99mTc-HMDP bone scan before and two to four days after an intravenous infusion of pamidronate. The number and activity of metastatic bone lesions were unchanged after pamidronate, even when the second bone scan was done only 24 hours after the pamidronate infusion. Our data suggest that emergency treatment of life-threatening hypercalcemia by intravenous pamidronate does not decrease the sensitivity of subsequent bone scanning done to detect bone metastases.