For the purpose of clinical consideration, malignant tumors of the kidney should be subdivided into two groups: those which have their origin in the renal cortex and those which arise from the renal pelvis. In a survey of 283 patients subjected to nephrectomy for carcinoma of the renal cortex at the Mayo Clinic, Judd and Hand1reported that seventy-four, or 26 per cent, were alive and well at the end of five years. Although such favorable results may be influenced by operative technic, they probably are affected more by the histologic character of the tumor and by the extent to which the malignant process has progressed. A study of the pathologic and clinical factors conducive to longevity in these cases is of much clinical interest. What are the data derived from histologic examination of the tumor, and what are the data observed on physical examination or in the course