A number of uncommon bone tumors and other pathologic changes of the skeleton which can resemble tumors have yet to be studied by angiography, and a final assessment of the value of this method for the examination of bone tumors is therefore, at present, impossible. In most tumors and suspected tumors, angiography provides information in addition to that yielded by plain films. In a few instances, a certain diagnosis may be made. In many cases of obscure osseous processes a confident diagnosis of malignant tumor is made on the basis of this method, and in others the angiographic appearances rule out a number of possible diagnoses. The method frequently indicates where a biopsy specimen should be taken and how an operation should be planned.