The main purpose of this note is to characterize a compact KahlerEinstein manifold in terms of curvature form. The curvature form Ω is an EndT valued differential form of type (1,1) which represents the curvature class of the manifold. We shall prove that the curvature form of a Kahler metric is the harmonic representative of the curvature class if and only if the Kahler metric is an Einstein metric in the generalized sense {g.s.) y that is, if the Ricci form of the metric is parallel. It is well known that a Kahler metric is an Einstein metric in the g. s. if and only if it is locally product (globally, if the manifold is simply connected and complete) of Kahler-Einstein metrics. We obtain an integral formula, involving the integral of the trace of some operators defined by the curvature tensor, which measures the deviation of a Kahler-Einstein metric from a Hermitian symmetric metric. In the final section we shall prove the uniqueness up to equivalence of Kahler-Einstein metrics in a simply connected compact complex homogeneous space. This result was proved by Berger [3] in the case of a complex projective space and our proof is completely different from Berger's.1. Throughout this paper we shall denote by M a compact Kahler manifold and by T and Γ* the holomorphic tangent bundle and the holomorphic cotangent bundle of M respectively. The real differentiable tangent bundle of M will be denoted by T& The vector space of smooth sections of a vector bundle F will be denoted by Γ(F). A section X of T is a complex vector field of holomorphic type or of type (1,0) and we denote by X the conjugate of X; X is a section of the conjugate bundle T of T. We denote by <, > the Hermitian metric in 7\ that is, if X, Y e Γ(T) f then
= g{X, Ϋ),where g denotes the Kahler metric in M. We have then