Although bone scintigraphy with 99mTc-MDP is a sensitive diagnostic method to detect bone metastasis, it is not specific for malignancy. A radioactive substance which accumulates specifically into metastatic lesions should be of value. 123I-IMP and bone scintigraphy with 99mTc-MDP were consecutively performed in patients with vertebral bone metastases from hepatocellular carcinoma and lumbar spondylosis deformans in a 7-day interval or shorter. The intensity of uptake was compared. Eighteen of the 20 metastatic lesions (90%) were classified as increased uptake areas in 123I-IMP scintigraphy. MDP-scintigraphy disclosed 16 metastatic lesions (80%), 9 as "hot" lesions (56%) and 7 as "cold" lesions (44%). 123I-IMP scintigraphy was negative in all 12 lesions of lumbar spondylosis deformans. Compared to MDP-scintigraphy, 123I-IMP scintigraphy was more sensitive in detecting vertebral bone metastases of hepatocellular carcinoma with smaller rates of false-positive and false-negative findings.