Urine cytology is of limited value in the diagnosis of renal cell carcinoma with reported detection rates of $0sim80%$. The aim of this study is to demonstrate the usefulness of urine cytology in renal cell carcinoma. In the eleven histologically proven cases of renal cell carcinoma, urinary smears were reevaluated. The cytologic results were as follows; positive for malignant cells in 3 cases(27%), suspicious in 2 cases(18%) and negative in 6 cases(55%). The average diameter of the tumor of the 5 cases reported as positive or suspicious for malignant cells was 9.7cm and 3 had invaded the renal pelvis. The other 6 tumors, reported as negative, were 5.7 cm in average diameter and one of them showed involvement of the renal pelvis. These results suggest that urine cytology is considered unsatisfactory in the early defection of renal cell carcinoma. However, careful examination of urinary smear could improve the detection rate especially in more advanced cases involving the renal pelvis as well as those of larger tumors.