This chapter presents the typical characteristics of focal atrial tachycardias and the systematic approach to diagnostics and therapy within the framework of invasive electrophysiology. With the help of this chapter, it should become clear how focal atrial tachycardias are defined, where they are located, what is important during the electrophysiological examination (such as the administration of drugs for provocation), and how the origin of focal atrial tachycardia can be identified using surface ECG and three-dimensional mapping techniques, and thus successfully ablated.