The initial enthusiasm for angiographic differentiation of renal tumor and cyst has matured into an attempt to differentiate a broad spectrum of medical and surgical lesions of the kidney. Pathologic lesions that mimic tumor, such as xanthogranulomatous pyelonephritis, abscesses, tuberculosis, and fibrolipomatosis, have been described with increasing frequency (1, 2, 6, 7). Marginal lobulations of the kidney, which may mimic tumor in normal kidneys, have been reported (4). Mass lesions of hypertrophied parenchyma or local nodular areas of residual normal parenchyma in diseased kidneys represent another form of pseudo-tumor. Unnecessary surgery, which could have been avoided by proper interpretation of the renal angiogram, has been performed in such instances. Case Reports Case I: A 47-year-old female was admitted to The Bronx-Lebanon Hospital Center with left flank pain and pyuria. There was an antecedent history of pyelonephritis extending back to childhood. A urogram revealed atrophic pyelonephritis bil...