The revision of the cemented femoral component to an uncemented revision implant is technically challenging and requires a careful removal of the cement mantle, with risk of complications including fracture. Alternatively, cemented femoral stems may be revised with the cement-in-cement or “tap-out-tap-in” technique. The cement mantle is preserved and prepared in indicated cases. This chapter discusses the indications for, approach to, and results of the tap-in tap-out technique in revision hip arthroplasty.