Extension of tumor into the vena cava occurs in 5 to 10 per cent of the cases of renal cell carcinomas. Of these cases 14 to 39 per cent may extend to or into the right atrium. Acceptable techniques for dealing with this situation include cross-clamping the atrium, using positive pressure ventilation and extracting the thrombus with a Fogarty or Foley catheter, and extracorporeal circulation or a cardiopulmonary bypass with open excision of the tumor extension. Since 1974 we have seen 2 men and 2 women, mean age 56 years, with clear cell renal carcinomas and supradiaphragmatic vena caval tumor extension (1 with additional pulmonary embolism). None had other evidence of metastatic disease determined on staging evaluation by celiac and renal angiography, liver scan, bone scan and chest tomography. Each patient was explored with the planned use of extracorporeal circulation or cardiopulmonary bypass, Greenfield vena caval filter insertion and standard radical nephrectomy. Resection was not done in 1 patient with biopsy proved tumor eroding through the right atrial wall. He died of disease in 8 months. Of the remaining 3 patients who had the tumors completely resected 1 is alive with recurrent disease in the retroperitoneum at 44 months, 1 died of metastatic disease to the bones and liver at 39 months, and 1 died 1 day postoperatively of technical complications with no evidence of residual disease at autopsy. In the absence of metastatic disease it seems reasonable to pursue a radical surgical approach in patients with renal cell carcinoma and supradiaphragmatic tumor thrombus. The use of extracorporeal circulation and post-extraction insertion of the Greenfield vena caval filter offers the surgeon the advantage of direct visualization and better vascular control in removing the thrombus, as well as protection from the possibility of post-extraction pulmonary embolism. With the combined use of these techniques, the previously hopeless situation for these patients has been improved.