Ion implanters for semiconductor applications use beamlines to transport ions generated in an ion source to wafers, and process chambers and end stations to handle wafers. In this chapter, we cover the basic theories and concepts applied to charged particle transport and implant control, including energy control, beam filtration and focusing, dosimetry, and implant angle and charge control, and we provide an overview of the complex control systems to ensure the ion implant remains within desired process windows.