For the modeling of charge response behavior in the organic field-effect-transistor (OFET) channel, the admittance of the OFET channel is measured from the two-terminal MIS structures. The channel is considered as an R-C network, and both the capacitance and loss of the measured admittance show good agreement with the model. The effective delay of the R-C network depends on the sheet resistance of the channel, the insulator capacitance, and the channel length. The maximum operating frequency of an OFET can be limited by this delay, because the channel charges cannot be induced completely within the delay time