THIS report describes a new technique for transplantation of the rat kidney from one animal to another by vascular anastomosis1. The rats were all members of an inbred line of the Lewis strain, originally obtained from a colony at the Wistar Institute. Skin grafts from one member of this colony to another are accepted uniformly. In the present experiment, the kidney donor weighed approximately 100 gm. It was first anaesthetized with ‘Cyclopal’ (Upjohn) and then the left kidney, including its vessels and ureter, was exposed through a midline incision. All the vascular branches of the abdominal aorta and vena cava, except the left renal vessels, were tied and divided from the level of the superior mesenteric artery to the origin of the iliac artery and vein.