Clear cell sarcoma is one of the rarely occurring renal tumors during childhood, and transvenous tumor extension into the right atrium is even more unusual. In this report, we describe the presentation, treatment, technique of complete resection, and outcome of a 23-month-old girl with clear cell sarcoma of the right kidney with cavo-atrial tumor thrombus. (c) 2006 Elsevier Inc. All rights reserved.