Modular and expandable endoprosthetic reconstruction of the child's extremity following bone tumor resection affords an opportunity for both limb salvage and progressive limb length equalization. This article discusses the rationale, advantages, disadvantages, and results of endoprosthetic bone reconstruction following tumor resections in the skeletally immature patient. In addition to an extensive literature review, an overview of the authors' results with this reconstructive option in 31 patients over the past 14 years is presented. This article will inform the reader of the current state of the art in endoprosthetic reconstruction of the immature patient and should allow clinicians to make more informed decisions regarding treatment options for their patients.