A photolithography process for the fabrication of organic thin-film transistor (OTFT) and integrated circuits will be presented. Fully encapsulated polythiophene OTFFs in the top-gate, bottom-gate, and dual-gate configurations have been demonstrated using this approach. Photolithography steps are incorporated for the definition of gate electrodes and source/drain contacts, isolation of transistors, and formation of vias and interconnects. These steps are vital to achieve device integration and to realize organic integrated circuits for applications such as flat panel displays and radio-frequency identification tags. The fabrication process is compatible with various substrates (e.g., glass and plastic), and enables the realization of discrete transistors and OTFT-based circuits through consecutive photolithographic steps and a tailored etch recipe for patterning of the polymer film. This article will provide a detailed examination of the fabrication approach, analyze the electrical performance of various photolithographically defined regioregular poly (3-hexylthiophene) OTFT structures, and explore the device and. circuit advantages of the photolithography strategy. (c) 2006 American Vacuum Society.