Abstract: Quantum well states in nonmagnetic metal films between magnetic layers are known to be important in spin-dependent transport. However, there are neither detailed theoretical studies on spin polarized quantum well states in ferromagnetic metal films nor clear experimental observations of electron tunneling through these states. In this paper we discuss the recent theoretical prediction by Zhong-Yi Lu, X.-G. Zhang and Pantelides［1］ on the resonant tunneling through Fe/MgO/FeO/Fe/Cr and other ferromagnetic quantum well states in magnetoresistance junctions. We further explain how the Δ1 band symmetry of Fe, Co, and Cr plays a crucial role in such resonant tunneling.