Flexibility will significantly expand the application scope of electronics, particularly large-area electronics. Over the last 10 years, printed organic electronic is believed to be one of the next major technological breakthroughs in the field of microelectronic and the use of printing technology to process organic field-effect transistors (OFETs) opens promising perspectives for low-cost, large-area circuits integrated on flexible, plastic substrates. With amorphous polymer-based thin film transistors acceptable electrical performances are now achieved with relatively good stability at ambient air. In the literature a lot of work has been devoted to study degradation of device characteristics under bias stress conditions but only few papers deal with the mechanical behavior. In this paper, we review our first reliability results obtained on flexible organic thin film transistors under mechanical stresses. The variations of electrical characteristics under bending tests, both in compression and tension, have been studied. Using specific equipment, we have also evaluated the reliability of transistors under cyclic bending tests. The stress dependency of the transfer characteristic deviates from the one observed for inorganic material like silicon.