The flexibility and versatility of organic field-effect transistors (OFETs) has opened up a wide range of new applications, such as in the field of wearable systems, bioelectronics, or as driving elements for individual pixels in a flat panel display. They have reached a remarkable level of maturity in terms of reproducibility, available material systems, processing technology, and fundamental understanding of the underlying physics. But OFETs are still limited in their performance. Vertical organic transistors try to address these challenges. They hold the promise of increasing the performance of flexible organic transistors while maintaining their low-cost advantage. Although vertical organic transistors have not been taken up for inorganic semiconductors, they may present some key advantages for organic semiconductors (OSCs). In this chapter, the various approaches of vertical organic transistors are summarized and the current understanding of their working mechanism is presented. Transistors with the highest performance are discussed briefly, which allows the reader to assess the strengths and weaknesses of particular approaches for different application fields.