Abstract. We present a sufficient condition for smoothness of bounded linear operators on Banach spaces for the first time. Let T, A ∈ B(X, Y), where X is a real Banach space and Y is a real normed linear space. We find sufficient condition for T ⊥ B A ⇔ T x⊥ B Ax for some x ∈ S X with T x = T , and use it to show that T is a smooth point in B(X, Y) if T attains its norm at unique (upto muliplication by scalar) vector x ∈ S X , T x is a smooth point of Y and sup y∈C T y < T for all closed subsets C of S X with d(±x, C) > 0. For operators on a Hilbert space H we show that T ⊥ B A ⇔ T x⊥ B Ax for some x ∈ S H with T x = T if and only if the norm attaining set M T = {x ∈ S H : T x = T } = S H 0 for some finite dimensional subspace H 0 and T Ho ⊥ < T . We also characterize smoothness of compact operators on normed spaces and bounded linear operators on Hilbert spaces.