Abstract. This paper is concerned with the space K w * (X * , Y ) of weak * to weak continuous compact operators from the dual space X * of a Banach space X to a Banach space Y . We show that if X * or Y * has the Radon-Nikodým property, C is a convex subset of K w * (X * , Y ) with 0 ∈ C and T is a bounded linear operator from X * into Y , then T ∈ C τc if and only if T ∈ {S ∈ C : S ≤ T } τc , where τc is the topology of uniform convergence on each compact subset of X, moreover, if T ∈ K w * (X * , Y ), here C need not to contain 0, then T ∈ C τc if and only if T ∈ C in the topology of the operator norm. Some properties of K w * (X * , Y ) are presented.