Organic field-effect transistors were fabricated with as the active material and various polymeric dielectrics as the gate insulator. The conduction parameters such as mobility, threshold voltage, subthreshold swing, the maximum density of surface states etc. were found out. The performances of the devices were compared with respect to the dielectric constant, thickness and surface morphology of the gate insulator and the leakage current through the gate. Out of the three dielectrics investigated viz. parylene-C, cyanoethylpullulan and poly(methylmethacrylate); parylene-C was found to be best suited for applications in organic FETs. (c) 2006 Springer Science + Business Media, Inc.