The ability to evaluate the composition and to precisely locate calcifications within renal masses resulted in more accurate evaluation of 21 calcified renal masses by computed tomography than by standard radiographic techniques. Of 11 solid tumors, computed tomography demonstrated a soft-tissue mass extending beyond the calcification in nine cases of renal cell carcinoma. Of 10 benign cystic lesions, all six lesions characterized by a uniform water-density center, calcification confined to the wall, and no detectable soft-tissue mass were benign cysts. Three additional cystic lesions (xanthogranulomatous pyelonephritis, multilocular cystic nephroma, and a cyst containing calcified debris) were believed to represent benign lesions prospectively due to the absence of a soft-tissue mass. Only peripherally calcified lesions with a central attenuation higher than accepted for benign cysts were indeterminate by computed tomography. The significance of the computed tomographic findings in terms of malignant potential and patient management is discussed.