When regional intraarterial infusion is applied in the treatment of malignant tumors it is essential to reach the tumor via all its major feeder vessels. In this study VX-2 carcinoma was implanted into the lower pole of the left kidney in 24 rabbits to investigate whether the renal capsular artery takes part in tumor feeding. The rabbits were divided into four groups that were followed for 8, 10, 12 or 14 days after tumor implantation. At that time the renal artery was ligated close to the kidney and subsequently silicone rubber on barium sulfate/gelatin suspension was injected into the capsular artery. The tissue was cleared, and the tumor carefully removed and examined microscopically for traces of silicone rubber. When barium sulfate had been injected, the kidney was examined radiographically in order to detect possible presence of contrast medium in the tumor. This study revealed no vascular supply to the implanted VX-2 carcinoma from the capsular artery when the tumor was confined intracapsularly, i.e., up to 12 days after tumor implantation in untreated rabbits.