We reviewed the clinical, radiographic, and where applicable, oncologic results of 112 consecutive allograft prosthetic composite reconstructions performed at Rush Presbyterian St Luke's Medical Center. The source of the bone defects included resection of a tumor, failure of a prior arthroplasty, and periprosthetic fracture. The patients having reconstruction after tumor resection achieved an average Enneking functional score of 28.3. Satisfactory clinical and radiographic results were obtained in 70% to 93%, depending on the group. Based on our experience, we have established a set of principles that should maximize functional results and minimize problems with allograft prosthetic composite arthroplasty.