Organic thin-film transistors (TFTs) are of interest for applications that require electronic functionality with low or medium complexity distributed over large areas on unconventional substrates, such as flexible plastics or paper. Generally these are applications in which the use of silicon devices and circuits is technically or economically not feasible, such as rollable flat-panel displays and large-area conformable sensor arrays. Active-matrix displays based on high-efficiency organic light-emitting diodes (OLEDs) require TFTs that can be operated with voltages of about 3 V. A promising approach to organic TFTs that can be operated with such low voltages are gate dielectrics based on a thin, plasma-grown AlOx layer in combination with an alkylphosphonic acid self-assembled monolayer (SAM); these hybrid gate dielectrics have a thickness of about 5 nm and a capacitance close to 1 µF/cm2. The static and dynamic performance of low-voltage organic p channel TFTs with AlOx/SAM gate dielectrics and relaxed lateral dimensions is already sufficient for flexible OLED displays with VGA resolution, where the TFTs operate with frequencies of a few tens of kilohertz. Increasing the performance of organic TFTs into the Megahertz regime requires scaling of the lateral TFT dimensions to 1 µm and below, which can be achieved, for example, by high-resolution inkjet-printing or stencil-mask techniques, ideally in combination with stable contact doping. Further advances are also required in the environmental stability of organic TFTs and in the development of high-mobility organic n channel TFTs to enable low-voltage, low power organic complementary circuits.