A review of 51 cases of renal cyst and 60 cases of renal cell carcinoma encountered at the Department of Radiology, Presbyterian-University Hospital, Pittsburgh, between the years 1957-1966, disclosed 11 cases of calcification in renal cell carcinoma and 1 case of calcification in a simple cyst. "Ring-like" or "rim-like" calcification appeared in 9 of 11 renal cell carcinomas, suggesting that this roentgen finding should be considered as a sign suggestive of malignancy of a renal mass.