This chapter deals with the general description of the Atucha II (about) 800MWe Pressurized Heavy Water Reactor in Argentina. The main design features and parameters of the Atucha II design are presented. In particular, based on requirements for the design of a Nuclear Power Plant established by International Atomic Energy Agency, the following topics are addressed: plant layout, reactor core and associated features, reactor coolant system, containment system, instrumentation and control, emergency control, emergency power supply, waste treatment and control systems, fuel handling and storage system, and radiation protection system.