The transport properties of (MeDH-TTP)(2)AsF6, which crystallized in the K-type structure, were investigated and found to be semiconductive with a small activation energy. ESR measurements suggested that the insulating state below 40 K should be anti ferromagnetic, similarly to the Mott transition system represented by quasi-two-dimensional K-ET [ET = bis(ethylenedithio)tetrathiafulvalene] salts.