Silsesquioxane polymers have been successfully used as the dielectric layer in organic field-effect transistors (FETs) deposited on robust, plastic substrates. Performance comparable to that found with silicon substrates having SiO2 as the active dielectric layer was observed with six p- and n- channel organic semiconductors. These organopolysiloxane materials can be deposited using conventional liquid coating technologies and are compatible with non-photolithographic microcontact printing. Their low curing temperature permits the use of a variety of low-cost plastic materials as substrates in FET devices. These findings have facilitated the realization of low-cost, large area plastic electronics.