Organic filed-effect transistor (OFETs) based on polycrystalline “octithiophene”has been realized. The current-voltage characteristics at low drain voltage has been used toderive the mobility of organic field effects transistors (OFETs). It appears that the datamust be corrected for the substantial source and drain contact resistance. The carriermobility is found to increase quasi linearly with gate voltage at room temperature. Thetemperature dependent measurements show that the mobility is thermally activated and becomespractically temperature independent at low temperatures. A model based on trappingmechanism, in which it is assumed that charge transport is limited by grain boundaries, hasbeen used to describe the carrier mobility in polycrystalline “octithiophene” thin filmtransistors measured at temperatures ranging from 10 K to 300 K.