This paper proposes actors as a model for mobile agents. Because of their intrinsic autonomy (thread integration) and behavior changing ability, added to asynchronous communication, actors are naturally mobile entities, and moving actors has no effect on their initial semantics. Then, we propose a standard API on top of Java and RMI, called JavAct, for distributed and mobile applications programming. JavAct is actor-based and allows nearly immediate and strong agent mobility. Mobile actors are localized by means of a forwarding chain technique. Network-level references of actors contribute to location independence of computations. Additionally, in this paper, we give an overview of some related programming systems.