This paper presents a duality between N=1 supersymmetric gauge theories and string theory on AdS5 × X5, where X5 is a five-dimensional Einstein manifold with five-form flux. The authors argue that string theory on AdS5 × X5 can be described by a certain N=1 superconformal field theory. They focus on the case where X5 is the conifold singularity, which is a homogeneous space T^{1,1} = (SU(2) × SU(2))/U(1). The conifold is a Calabi-Yau threefold with SU(2) × SU(2) × U(1) symmetry. The authors show that the infrared limit of the world volume theory on coincident D3-branes placed at a conical singularity of a non-compact Calabi-Yau threefold corresponds to a superconformal field theory. They also find that the N=2 superconformal theory corresponding to S^5/Z2 flows to the N=1 IR fixed point corresponding to T^{1,1}. The superpotential of the N=1 theory is shown to be odd under Z2 and corresponds to a blow-up mode of the orbifold. The authors also compare the superconformal field theory to orbifold theories and show that the blowup of the fixed circle of S^5/Z2 gives T^{1,1}. They conclude that the two models are topologically equivalent as S^3 bundles over S^2.This paper presents a duality between N=1 supersymmetric gauge theories and string theory on AdS5 × X5, where X5 is a five-dimensional Einstein manifold with five-form flux. The authors argue that string theory on AdS5 × X5 can be described by a certain N=1 superconformal field theory. They focus on the case where X5 is the conifold singularity, which is a homogeneous space T^{1,1} = (SU(2) × SU(2))/U(1). The conifold is a Calabi-Yau threefold with SU(2) × SU(2) × U(1) symmetry. The authors show that the infrared limit of the world volume theory on coincident D3-branes placed at a conical singularity of a non-compact Calabi-Yau threefold corresponds to a superconformal field theory. They also find that the N=2 superconformal theory corresponding to S^5/Z2 flows to the N=1 IR fixed point corresponding to T^{1,1}. The superpotential of the N=1 theory is shown to be odd under Z2 and corresponds to a blow-up mode of the orbifold. The authors also compare the superconformal field theory to orbifold theories and show that the blowup of the fixed circle of S^5/Z2 gives T^{1,1}. They conclude that the two models are topologically equivalent as S^3 bundles over S^2.