One hundred and sixty patients having bronchogenic carcinoma were evaluated for bone metastasis by means of 99mTc-monodiphosphate bone scanning, correlative radiographic bone survey and their clinical findings. In all patients, diagnosis was histologically proved. Bone scan demonstrated the possible evidence of bone metastasis in 75 patients (46.9%) and radiography, in 29 patients (18.1%). False negative was noted in 1 patient-Bone scan correlated with radiography in 37.3%, and with accompanying bone pain in 52% of the patients. But there was no correlation with the level of serum calcium, inorganic phos- phorus and alkaline phosphatase. In connection with their clinical stages before scanning, bone scans were positive in 33.3% of clinical stage I, 10.8% of clinica1 stage II and 54.1% of clinical stage III. Our Study suggests that bone scanning with 99m-monodiphosphate detected early bone metastasis in patients with bronchogenic carcinoma before their lesions became evident clinically or radiographically, and also important to determine operability.