In this paper we describe printing methods for transferring single-walled carbon nanotubes (SWNTs) from high-temperature growth substrates to flexible, low-cost plastic supports. Thin-film transistors (TFTs) built with networks of transferred SWNTs grown by chemical vapor deposition show good performance-mobilities and on/off current ratios similar to those of devices fabricated on the growth substrates for a wide range of channel lengths. Bending tests on these TFTs show that their output current varies only in a narrow (+/- 5%) range, even for bend radii that induce surface strains larger than 1%. Similar structures evaluated under sharp folding, with strains larger than 20%, show that the SWNT networks are operational even under extreme bending conditions. This level of mechanical robustness, the good electrical performance, and optical transparency make transferred SWNT networks an attractive type of electronic material for applications in macroelectronics, sensors, and other systems that require wide area coverage and unusual substrates. (c) 2005 American Institute of Physics.