We prove new results on the stability of the absolutely continuous spectrum for perturbed Stark operators with decaying or satisfying certain smoothness assumption perturbation. We show that the absolutely continuous spectrum of the Stark operator is stable if the perturbing potential decays at the rate (1 + x)-1/3-ε or if it is continuously differentiate with derivative from the Holder space Ca(R), with any α > 0. © 1999 American Mathematical Society.