We demonstrate a high-performance organic thin-film transistor array fabricated on a flexible paper substrate. As a water and chemical barrier layer, 6-/spl mu/m-thick parylene has been coated on the paper substrate by using the vacuum deposition. The parylene layer protects the paper substrate from becoming damp during the wet chemical process. Using poly (3-hexylthiophene) as an active layer, a high-performance organic transistor with field effect mobility up to 0.086 cm/sup 2//V/spl middot/s and an on/off ratio of 10/sup 4/ can be achieved. Organic transistors built on a cheap paper substrate open a channel for future applications in flexible and disposable electronics with extremely low-cost.