We successfully have used nephrotomography as a further diagnostic test to rule out the possibility that an avascular renal mass, demonstrated initially by selective renal angiography, represents an avascular solid renal tumor. The important diagnostic sign is the visualization of a definite thickening of the tumor wall on good-quality nephrotomographic studies. Most of these solid avascular tumors have proved to be papillary adenocarcinoma. Other diagnostic tests, such as cyst puncture, are excellent studies but simplicity, safety, and accuracy (with adequate examinations) are important considerations. A renal cyst may be diagnosed with confidence by using good-quality nephrotomographic studies without the necessity for renal angiography.