Jaecheol Lee. 2001. Antecedent Contained Deletion and LF Pied Piping. Studies in Modern Grammar 24, 67-90. In this paper, we prove that LF pied-piping is required for the resolution of Antecedent Contained Deletion(ACD), and that the theory-internal motives for the LF pied-piping results from economy considerations; LF convergence and the Last Resort. ACD resolution requires LF pied piping of an entire phrase out of categories that contain it. We argue that the LF pied-piping movements by Quantifier Raising and Rightward movement are triggered for the purpose of resolving the infinite regress problem in ACD configuration. Both movements are necessary to satisfy Full Interpretation at LF. We propose that QR is driven by a QU-feature, which triggers LF pied-piping of a quantificational expression in ACD configuration. The checking of QU-feature arises because the interpretively redundant QU-features on QP and its target are not allowed at the interface, which result in the violation of the principle of full interpretation. Rightward movement is driven by the Last Resort, chosen only when QR cannot occur in ACD construction.