Suppose g(X) is an unbiased estimator of ƞ(θ), V is ancillary and δ2(V, θ) = Var θ(g|V). Let ʘ1 = { θ ϵ ʘ : ƞ(θ) ≠ 0 or E[1/δ(V, θ)] < ∞}. Then, a necessary condition for g to be the UMVUE of ƞ(θ) is that for θ ϵ ʘ1, δ2(V, θ) is independent of V , w.p. 1.