Introduction. We shall prove an abstract theorem on the duality of vector lattices. It is powerful and general enough to yield quickly the duality of both the classical examples of concrete vector lattices as well as various abstract analogs of these lattices. The theorem treats the duality of L1 and Lo, so as to exhibit the relation of their duality to the duality of the Lp spaces for 1 xa >p= xlaa =x, then limf(xa) =f(x). This implies that f is bounded in the sense that the set {f(x): 0