CT findings of 10 cases of transitional cell carcinoma with renal parenchymal involvement were reviewed. CT showed a low-density mass with varying degrees of renal parenchymal involvement. Intrarenal transitional cell carcinomas were characterized by preserved renal contour with abnormalities of the collecting system such as obliteration, entrapment in the tumor, dilatation, and intraluminal mass. Obliteration of the renal sinus fat and poorly defined tumor margin were other characteristic CT features. This study indicated that CT is useful for differentiating transitional cell carcinomas with renal parenchymal involvement from renal cell carcinomas.