OBJECTIVE Extraperitoneal renal transplantation is not routine in small recipients, in whom transperitoneal engraftment is the norm. The outcome of extraperitoneal placement of renal allografts in children weighing less than 15 kg. was evaluated at 2 institutions. METHODS We retrospectively reviewed all pediatric renal transplantations at 2 institutions from 1988 to 2000 and identified 29 children 14 to 72 months old (mean age 29.2) weighing less than 15 kg. (range 8 to 14.8, mean 11.2). All children underwent allograft placement extraperitoneally via a modified Gibson and low midline retroperitoneal incision in 27 and 2, respectively. A concurrent procedure was done via the same incision during 2 ipsilateral and 2 bilateral nephrectomies. RESULTS Of the 29 patients 25 have a functioning renal allograft. In 2 cases the initial allograft was lost due to early postoperative thrombosis and acute rejection in 1 each. Two patients with a functioning allografts died of medical complications greater than 2 years after transplantation. One child required reexploration secondary to fascial dehiscence and an additional recipient required pyeloureterostomy due to ureteral necrosis after living related donor transplantation. CONCLUSIONS Extraperitoneal renal transplantation is technically feasible in children who weigh less than 15 kg. This approach preserves the peritoneal cavity, limits potential gastrointestinal complications and allows the confinement of potential surgical complications, such as bleeding and urinary leakage. In addition, this approach provides complete access to the retroperitoneum to enable concurrent retroperitoneal surgery, such as nephrectomy, to be performed safely. We recommend that extraperitoneal renal engraftment should become routine in children weighing less than 15 kg. rather than using the more common transperitoneal approach for allograft placement.