Renal cell carcinoma (RCC) is rare neoplasm and rarely extends to IVC. Perinephric and venous system invasion is an important prognostic sign for RCC. The tumor may grow intraluminally into the renal vein and Inferior Vena Cava (IVC) as an extension of primary tumor. In this report, we present two unusual case of venous system involvement, invasion of RCC into SVC. RCC with tumor thrombus extension into the IVC remains a difficult operative challenge. However surgical intervention should be performed. Our cases were successfully operated and their post operative recovery was uneventful.