Scintigraphy with thallium-201 was performed on 22 patients in whom a solitary abnormality in bone was suspected of being malignant. In three patients, an additional lesion was subsequently identified. Preferential TI-201 uptake was found in 7 of 8 malignant lesions, but was absent in 16 of 17 abnormalities that proved to be benign. The use of TI-201 scanning is considered to offer high negative predictive value in the assessment of possible malignant change in bone.