Printing semiconductor devices under ambient atmospheric conditions is a promising method for the large-area, low-cost fabrication of flexible electronic products. However, processes conducted at temperatures greater than 150 degrees C are typically used for printed electronics, which prevents the use of common flexible substrates because of the distortion caused by heat. The present report describes a method for the room-temperature printing of electronics, which allows thin-film electronic devices to be printed at room temperature without the application of heat. The development of pi-junction gold nanoparticles as the electrode material permits the room-temperature deposition of a conductive metal layer. Room-temperature patterning methods are also developed for the Au ink electrodes and an active organic semiconductor layer, which enables the fabrication of organic thin-film transistors through room-temperature printing. The transistor devices printed at room temperature exhibit average field-effect mobilities of 7.9 and 2.5 cm(2) V-1 s(-1) on plastic and paper substrates, respectively. These results suggest that this fabrication method is very promising as a core technology for low-cost and high-performance printed electronics.