The conversion of a patient with a Girdlestone resection arthroplasty to a revision total hip arthroplasty poses several challenges in adult reconstructive surgery. Ever since Dr. Girdlestone’s original description of his procedure in 1928, resection arthroplasty has evolved over the past century to provide a solution for complex problems in poor operative candidates. However, as patients are left with only a crude articulation between the proximal femur and acetabulum, this can lead to a substantial limb length discrepancy, abductor muscle dysfunction, dependence on a walking aid, and a poor quality of life. As a result, patients often request conversion total hip arthroplasty to restore function and independence. In this chapter, after a brief historical perspective, the indications for conversion and frequent intraoperative challenges are discussed. Furthermore, the authors describe their preferred technique to convert a Girdlestone resection arthroplasty to a revision total hip arthroplasty, supplementing the text with intraoperative pictures and images.