In order to establish criteria for distinguishing between occult fracture and metastases, we have reviewed 52 records of cancer patients and 24 of rib fracture patients referred for bone scanning. In 52 patients with biopsy-proven malignancy, multiple linear increased uptake of the ribs was found in 32 cases(61.5%), and was the most common finding. In 24 patients with rib fracture, all but 1 had fecal increased uptake of the ribs, and lesions almost always aligned in a row. By analyzing the appearance of rib lesions in total 76 patients, it was concluded that there is a high probability that rib lesions detected by bone scanning are bony metastases if 1) they are multiple linear as opposed to fecal, and 2) they are not aligned in the same location