The precise diagnosis of carcinoma of the kidney is of particular importance because renal mass lesions are frequently encountered which require nephrectomy if malignant, and renal tissue conservation if benign. The diagnostic problems include those of differentiating benign from malignant tumors and tumors from cysts. Delineation of the extent of tumors is also essential for treatment planning and prognostic implications. Although the sequence of diagnostic imaging procedures utilized in suspected renal mass lesions varies somewhat depending on the clinical presentation, the following techniques are frequently employed until the relevant questions have been answered: urography, ultrasound and/or computed tomography, cyst puncture and contrast injection, angiography, and renal venography. These non-operative methods usually clarify the nature and extent of renal mass lesions and therefore have a major effect on therapy. A logical, systematic approach to their application avoids duplication and achieves appropriate diagnosis most rapidly.