BACKGROUND We report a technique for extending the distal aorta to facilitate the transplantation of en bloc horseshoe kidneys. METHODS En bloc horseshoe kidneys can be transplanted by a technique that is analogous to the en bloc transplantation of small pediatric kidneys. However, the horseshoe kidney's isthmus prevents ascent of the kidney, and the fused lower poles stay below the level of the inferior mesenteric artery. Therefore, the distal aorta is behind the isthmus. Extending the distal aorta produces adequate vessel length to simplify en bloc transplantation of horseshoe kidneys. The extra aortic length is obtained by spatulating the distal common iliac arteries on their medial surfaces and bringing them together as a "pair of pants" for about 1.5 cm. This produces an arterial conduit that branches into the left and right common iliac arteries and then rejoins at the distal aorta. The aortic extension produces a useable vascular conduit that can be anastomosed to the recipient's external iliac artery. The distal inferior vena cava is anastomosed to the external iliac vein. We used this technique in 1 patient. The transplanted kidney made urine promptly and was providing normal function with a serum creatinine of 1.1 mg/dL. CONCLUSIONS It is preferable to transplant some horseshoe kidneys en bloc using the distal aorta and inferior vena cava for vascular anastomoses. This technique extends the distal aorta and provides adequate vessel length to facilitate en bloc transplantation.