In this paper we demonstrate the applicability of the unified model and parameter extraction method (UMEM), previously developed by us, to organic thin film transistors, OTFTs. The UMEM, which has been previously used with a-Si:H, polysilicon and nanocrystalline TFTs, provides a much rigorous and accurate determination of main electrical parameters of organic TFTs than previous methods. Device parameters are extracted in a simple and direct way from the experimental measurements, with no need of assigning predetermined values to any other model parameter or using optimization methods. The method can be applied to both experimental and simulated characteristics of organic TFTs, having different geometries and mobility. It provides a very good agreement between transfer, transconductance and output characteristics calculated using parameter values obtained with our extraction procedure and experimental curves. Differences in mobility behavior, as well as other device features that can be analyzed using UMEM are discussed. (c) 2005 Elsevier Ltd. All rights reserved.