[en] The Ministry of the Russian Federation for Atomic Energy (MINATOM) and the US Department of Energy (DOE) are engaged in joint, cooperative efforts to reduce the likelihood of nuclear proliferation by enhancing Material Protection, Control and Accounting (MPC ampersand A) systems in both countries. Mayak Production Association (MPA) is a major Russian nuclear enterprise within the nuclear complex that is operated by MINATOM. This paper describes the nature, scope, and status of the joint, cooperative efforts to enhance existing MPC ampersand A systems at MPA. Current cooperative efforts are focused on enhancements to the existing MPC ampersand A systems at four plants that are operated by MPA and that produce, process, handle and/or store proliferation-sensitive nuclear materials