The results of total skeletal scintigraphy with technetium 99m-labeled diphosphonate in 200 patients with biopsy-proven primary cancer demonstrated abnormalities in 114; 57 had normal roentgenograms. In 32 of the 57 patients, the abnormalities were ascribed to malignant lesions. This is a false-negative rate of 17% for the roentgenographic examinations. Only three patients had abnormal roentgenograms but normal scans, a yield of 1.6% false-negative scans. In a comparison of scan and roentgenographic findings with the skeleton divided into 12 regions, 119 of 160 abnormalities seen on scans but not on roentgenograms were attributed to tumor. Only five of 17 regions that were abnormal on roentgenogram but not on scans were unexplained false-negative findings. Thus, on a regional basis, the yields of false-negative roentgenograms and scans were 9.1% and 0.4%, respectively.