The realization and performance of a novel organic field-effect transistorthe organic junction field-effect transistor (JFET)is discussed. The transistors are based on the modulation of the thickness of a depletion layer in an organic pin junction with varying gate potential. Based on numerical modeling, suitable layer thicknesses and doping concentrations are identified. Experimentally, organic JFETs are realized and it is shown that the devices clearly exhibit amplification. Changes in the electrical characteristics due to a variation of the intrinsic and the p-doped layer thickness are rationalized by the numerical model, giving further proof to the proposed operational mechanism.