Composite tissue transplantation has emerged as a viable alternative to prosthetics and complex reconstructive surgery. Thus far it is reserved for cases which cannot be effectively reconstructed and where it offers some benefits over prostheses. It has been used in the upper extremity with encouraging results and, most recently, in the face. This report outlines what is believed to be the first such use in the lower extremity. A normal lower limb in a 3-month-old ischiopagus twin who was not going to survive was transplanted to the appropriate pelvic position, revascularized, and reinnervated in an otherwise healthy sister. The limb survived and, because of the immune compatibility, did not require immune suppressive therapy. The return of muscle function in the transplanted limb is encouraging. The transplanted limb appears to be fully sensate. In addition to reinnervation, the limb is now spontaneously under the cortical control of the recipient.