The rationale and principles of a logical approach to the radiologic diagnosis of the renal mass are presented. The advantages and limitations of plain roentgenography, intravenous urography, drip infusion pyelography, retrograde pvelography, renal scanning, nephrotomographv, aortography, selective renal arteniography, and percutaneous cyst puncture are discussed. A technique for cyst puncture utilizing image intensification is described. [see figure in the PDF file] With this approach, surgery can be definitive rather than exploratory. The patient with hypernephroma is, thus, given a greater chance for cure and unnecessary surgery is avoided in the patient with a cyst.